From c6a0c7f6764d06d128176ac39e6c5f1d899fd607 Mon Sep 17 00:00:00 2001
From: Fabricio Giglio <58532944+gigliof@users.noreply.github.com>
Date: Sun, 10 May 2026 23:50:20 +0200
Subject: [PATCH] Add piano fingering generation and display via pianoplayer,
 fix silent audio on first load

---
 backend/services/pianoplayer_svc.py           |  52 ++-
 .../FallingNotes/FallingNotesRenderer.ts      |  23 +-
 .../FallingNotes/FallingNotesView.tsx         |  51 ++-
 .../components/Transport/SettingsPanel.tsx    |  65 +++-
 frontend/src/engine/AudioEngine.ts            |  67 +++-
 frontend/src/engine/SyncEngine.ts             | 116 +++++--
 frontend/src/store/useAppStore.ts             | 308 ++++++++++++++----
 frontend/src/views/PracticeView.tsx           |  22 +-
 8 files changed, 542 insertions(+), 162 deletions(-)

diff --git a/backend/services/pianoplayer_svc.py b/backend/services/pianoplayer_svc.py
index d1dfb87..7bc8d13 100644
--- a/backend/services/pianoplayer_svc.py
+++ b/backend/services/pianoplayer_svc.py
@@ -1,8 +1,8 @@
 """
 pianoplayer service: annotate MusicXML with fingering (Parncutt algorithm).
 
-Note: defusedxml.defuse_stdlib() is called in main.py before this module
-is imported, so xml.etree (used by music21 internally) is already patched.
+Uses the pianoplayer v3 API (run_annotate) which handles part routing and
+hand assignment internally.
 """
 import asyncio
 import os
@@ -28,11 +28,12 @@ async def annotate_fingering(musicxml: str) -> str:
 
 
 def _annotate(musicxml: str) -> str:
-    from pianoplayer.hand import RightHand, LeftHand
-    import music21
+    import io
+    import contextlib
+    from pianoplayer.core import run_annotate
 
     xml_path = None
-    out_tmp_name = None
+    out_path = None
     try:
         with tempfile.NamedTemporaryFile(
             suffix=".xml", delete=False, mode="w", encoding="utf-8"
@@ -40,37 +41,24 @@ def _annotate(musicxml: str) -> str:
             f.write(musicxml)
             xml_path = f.name
 
-        score = music21.converter.parse(xml_path)
-
-        # pianoplayer works on individual parts
-        for part in score.parts:
-            notes = list(part.flatten().notes)
-            if not notes:
-                continue
-
-            # Determine left / right hand by average register
-            avg_pitch = sum(
-                n.pitch.midi for n in notes if hasattr(n, "pitch")
-            ) / max(len(notes), 1)
-            hand_cls = RightHand if avg_pitch >= 60 else LeftHand
-
-            try:
-                hand = hand_cls(score, 0)
-                hand.autodepth = False
-                hand.verbose = False
-                hand.generate(part=part.id if hasattr(part, "id") else 0)
-            except Exception:
-                pass  # pianoplayer can fail on complex scores; skip gracefully
-
         out_tmp = tempfile.NamedTemporaryFile(suffix=".xml", delete=False)
         out_tmp.close()
-        out_tmp_name = out_tmp.name
-        score.write("musicxml", fp=out_tmp_name)
+        out_path = out_tmp.name
 
-        return Path(out_tmp_name).read_text(encoding="utf-8")
+        # Suppress Rich progress/summary output so server logs stay clean.
+        with contextlib.redirect_stdout(io.StringIO()), contextlib.redirect_stderr(io.StringIO()):
+            run_annotate(
+                xml_path,
+                outputfile=out_path,
+                n_measures=1000,
+                auto_routing=True,  # let pianoplayer detect which part is L/R
+                quiet=True,
+            )
+
+        return Path(out_path).read_text(encoding="utf-8")
 
     finally:
         if xml_path:
             Path(xml_path).unlink(missing_ok=True)
-        if out_tmp_name:
-            Path(out_tmp_name).unlink(missing_ok=True)
+        if out_path:
+            Path(out_path).unlink(missing_ok=True)
diff --git a/frontend/src/components/FallingNotes/FallingNotesRenderer.ts b/frontend/src/components/FallingNotes/FallingNotesRenderer.ts
index 8998b00..734e930 100644
--- a/frontend/src/components/FallingNotes/FallingNotesRenderer.ts
+++ b/frontend/src/components/FallingNotes/FallingNotesRenderer.ts
@@ -244,6 +244,9 @@ class NoteBar {
   private label: PIXI.Text;
   /** Whether this bar's label should be shown at all (text non-empty AND bar big enough). */
   private labelWanted = false;
+  /** Cached at configure() time so relabel() can recompute labelWanted without re-rendering the bar. */
+  private barWidth = 0;
+  private barHeight = 0;
   note: NoteEvent | null = null;
   active = false;
   impactFired = false;
@@ -283,6 +286,8 @@ class NoteBar {
     this.active = true;
     this.impactFired = false;
     this.baseColor = baseColor;
+    this.barWidth = barWidth;
+    this.barHeight = barHeight;
     this.container.visible = true;
     this.container.x = x;
     this.container.y = startY;
@@ -325,6 +330,13 @@ class NoteBar {
     this.label.visible = this.labelWanted;
   }
 
+  /** Update just the label text on an already-configured bar. Cheap: no re-rendering of bg. */
+  relabel(labelText: string) {
+    this.label.text = labelText;
+    this.labelWanted = labelText.length > 0 && this.barHeight > 6 && this.barWidth > 7;
+    this.label.visible = this.labelWanted;
+  }
+
   /** Keep label clamped within the visible portion of the bar (for very tall notes). */
   updateLabelY(containerY: number, barHeight: number, viewportHeight: number) {
     if (!this.labelWanted) {
@@ -362,6 +374,7 @@ export interface FallingNotesOptions {
   height: number;
   viewportSeconds: number;
   fallingNotesLabelMode?: NoteLabelMode;
+  /** When true, append the assigned finger digit to each note bar's label */
   showFingering: boolean;
   showHandColors: boolean;
   useFlats: boolean;
@@ -983,9 +996,13 @@ export class FallingNotesRenderer {
       ("useFlats" in opts && opts.useFlats !== this.opts.useFlats) ||
       ("fallingNotesLabelMode" in opts &&
         opts.fallingNotesLabelMode !== this.opts.fallingNotesLabelMode) ||
-      ("showFingering" in opts && opts.showFingering !== this.opts.showFingering) ||
       ("showNoteOutline" in opts && opts.showNoteOutline !== this.opts.showNoteOutline);
 
+    // Fingering toggle is cheaper - re-label active bars in place rather than
+    // resetting (which would briefly clear all bars from the screen).
+    const fingeringChanged =
+      "showFingering" in opts && opts.showFingering !== this.opts.showFingering;
+
     Object.assign(this.opts, opts);
     if (!this._initialized) return;
 
@@ -993,6 +1010,10 @@ export class FallingNotesRenderer {
       for (const g of this.gradientCache.values()) g.destroy();
       this.gradientCache.clear();
       this.reset();
+    } else if (fingeringChanged) {
+      for (const [, bar] of this.active) {
+        if (bar.note) bar.relabel(this.noteLabel(bar.note));
+      }
     }
     if ("showGrid" in opts) this.gridLayer.visible = !!opts.showGrid;
     if ("impactStyle" in opts) {
diff --git a/frontend/src/components/FallingNotes/FallingNotesView.tsx b/frontend/src/components/FallingNotes/FallingNotesView.tsx
index 22de7c0..fb07ade 100644
--- a/frontend/src/components/FallingNotes/FallingNotesView.tsx
+++ b/frontend/src/components/FallingNotes/FallingNotesView.tsx
@@ -17,12 +17,16 @@ export function FallingNotesView() {
   const accuracy = useAccuracy(midiEnabled && (status === "playing" || status === "paused"));
 
   const measureStarts = useMemo(
-    () => doc ? computeMeasureSeconds(doc.timeSignatures, doc.tempoMap, doc.ppq, doc.totalDuration) : [],
+    () =>
+      doc
+        ? computeMeasureSeconds(doc.timeSignatures, doc.tempoMap, doc.ppq, doc.totalDuration)
+        : [],
     [doc]
   );
 
   const beatStarts = useMemo(
-    () => doc ? computeBeatSeconds(doc.timeSignatures, doc.tempoMap, doc.ppq, doc.totalDuration) : [],
+    () =>
+      doc ? computeBeatSeconds(doc.timeSignatures, doc.tempoMap, doc.ppq, doc.totalDuration) : [],
     [doc]
   );
 
@@ -38,7 +42,7 @@ export function FallingNotesView() {
       height,
       viewportSeconds: settings.viewportSeconds,
       fallingNotesLabelMode: settings.fallingNotesLabelMode,
-      showFingering: settings.showFingering,
+      showFingering: settings.showFingering && settings.showFingeringOnNotes,
       showHandColors: settings.showHandColors,
       useFlats: settings.useFlats,
       noteFilter: settings.noteFilter,
@@ -103,7 +107,7 @@ export function FallingNotesView() {
     rendererRef.current?.setOptions({
       viewportSeconds: settings.viewportSeconds,
       fallingNotesLabelMode: settings.fallingNotesLabelMode,
-      showFingering: settings.showFingering,
+      showFingering: settings.showFingering && settings.showFingeringOnNotes,
       showHandColors: settings.showHandColors,
       useFlats: settings.useFlats,
       noteFilter: settings.noteFilter,
@@ -127,6 +131,7 @@ export function FallingNotesView() {
     settings.viewportSeconds,
     settings.fallingNotesLabelMode,
     settings.showFingering,
+    settings.showFingeringOnNotes,
     settings.showHandColors,
     settings.useFlats,
     settings.noteFilter,
@@ -151,7 +156,10 @@ export function FallingNotesView() {
     if (!doc || !settings.scrollToSeek) return;
     // Seek forward/backward by 30% of the viewport window per scroll tick
     const delta = (e.deltaY > 0 ? 1 : -1) * settings.viewportSeconds * 0.3;
-    const next = Math.max(0, Math.min(doc.totalDuration, useAppStore.getState().currentSeconds + delta));
+    const next = Math.max(
+      0,
+      Math.min(doc.totalDuration, useAppStore.getState().currentSeconds + delta)
+    );
     seek(next);
   };
 
@@ -162,19 +170,25 @@ export function FallingNotesView() {
       onWheel={handleWheel}
       style={{
         minHeight: 200,
-        background: "radial-gradient(ellipse at 50% 100%, rgba(147,51,234,0.07) 0%, transparent 65%), var(--color-notes-bg)",
+        background:
+          "radial-gradient(ellipse at 50% 100%, rgba(147,51,234,0.07) 0%, transparent 65%), var(--color-notes-bg)",
         borderTop: "1px solid var(--color-notes-border)",
       }}
     >
       <canvas ref={canvasRef} style={{ display: "block", width: "100%", height: "100%" }} />
 
-      {midiEnabled && (accuracy.correct + accuracy.wrong + accuracy.missed) > 0 && (
+      {midiEnabled && accuracy.correct + accuracy.wrong + accuracy.missed > 0 && (
         <div
           className="absolute top-2 left-2 z-10 pointer-events-none text-xs px-2 py-0.5 rounded-full font-medium"
           style={{
-            background: accuracy.score >= 80 ? "rgba(34,197,94,0.12)" : accuracy.score >= 50 ? "rgba(234,179,8,0.12)" : "rgba(239,68,68,0.12)",
-            color:      accuracy.score >= 80 ? "#4ade80"               : accuracy.score >= 50 ? "#eab308"              : "#ef4444",
-            border:     "1px solid currentColor",
+            background:
+              accuracy.score >= 80
+                ? "rgba(34,197,94,0.12)"
+                : accuracy.score >= 50
+                  ? "rgba(234,179,8,0.12)"
+                  : "rgba(239,68,68,0.12)",
+            color: accuracy.score >= 80 ? "#4ade80" : accuracy.score >= 50 ? "#eab308" : "#ef4444",
+            border: "1px solid currentColor",
           }}
         >
           <TargetIcon /> {accuracy.score}%
@@ -187,9 +201,18 @@ export function FallingNotesView() {
 // ── Icons ─────────────────────────────────────────────────────────────────────
 
 const TargetIcon = () => (
-  <svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" style={{ display: "inline", verticalAlign: "middle", marginBottom: 1 }} aria-hidden="true">
-    <circle cx="12" cy="12" r="9"/>
-    <circle cx="12" cy="12" r="5"/>
-    <circle cx="12" cy="12" r="2" fill="currentColor" stroke="none"/>
+  <svg
+    width="11"
+    height="11"
+    viewBox="0 0 24 24"
+    fill="none"
+    stroke="currentColor"
+    strokeWidth="2"
+    style={{ display: "inline", verticalAlign: "middle", marginBottom: 1 }}
+    aria-hidden="true"
+  >
+    <circle cx="12" cy="12" r="9" />
+    <circle cx="12" cy="12" r="5" />
+    <circle cx="12" cy="12" r="2" fill="currentColor" stroke="none" />
   </svg>
 );
diff --git a/frontend/src/components/Transport/SettingsPanel.tsx b/frontend/src/components/Transport/SettingsPanel.tsx
index 0f49920..b784eb6 100644
--- a/frontend/src/components/Transport/SettingsPanel.tsx
+++ b/frontend/src/components/Transport/SettingsPanel.tsx
@@ -430,7 +430,13 @@ function ResetButton() {
 // ── Main component ────────────────────────────────────────────────────────────
 
 export function SettingsPanel({ open, onClose }: { open: boolean; onClose: () => void }) {
-  const { settings, updateSettings } = useAppStore();
+  const {
+    settings,
+    updateSettings,
+    document: doc,
+    isGeneratingFingering,
+    generateFingering,
+  } = useAppStore();
 
   // Computes the inline style for range inputs.
   // Sets --fill-pct so the CSS gradient draws the correct filled/unfilled split.
@@ -1084,6 +1090,63 @@ export function SettingsPanel({ open, onClose }: { open: boolean; onClose: () =>
 
           {/* ── Overlays ───────────────────────────────────────────────────── */}
           <Section title="Overlays">
+            <Row
+              label="Finger numbers"
+              sublabel="1-5 hints on the piano keyboard"
+              title="Show finger number hints on the piano keyboard"
+            >
+              {doc?.musicXml && (
+                <button
+                  onClick={() => void generateFingering()}
+                  disabled={isGeneratingFingering}
+                  title={
+                    doc.fingeringVersion === "auto"
+                      ? "Regenerate finger numbers using the Parncutt algorithm"
+                      : "Generate finger number hints using the Parncutt algorithm"
+                  }
+                  style={{
+                    fontSize: 11,
+                    padding: "3px 9px",
+                    borderRadius: 5,
+                    border: "1px solid var(--color-border)",
+                    background: "var(--color-surface-2)",
+                    color: isGeneratingFingering
+                      ? "var(--color-text-muted)"
+                      : "var(--color-accent)",
+                    cursor: isGeneratingFingering ? "wait" : "pointer",
+                    whiteSpace: "nowrap",
+                    flexShrink: 0,
+                    opacity: isGeneratingFingering ? 0.6 : 1,
+                  }}
+                >
+                  {isGeneratingFingering
+                    ? "Generating…"
+                    : doc.fingeringVersion === "auto"
+                      ? "Regenerate"
+                      : "Generate"}
+                </button>
+              )}
+              <Toggle
+                active={settings.showFingering}
+                onClick={() => updateSettings({ showFingering: !settings.showFingering })}
+              />
+            </Row>
+
+            {settings.showFingering && (
+              <Row
+                label="Also on falling notes"
+                sublabel="appends digit to each note bar"
+                title="Also overlay finger digits on the falling-note bars (off by default - visually busier)"
+              >
+                <Toggle
+                  active={settings.showFingeringOnNotes}
+                  onClick={() =>
+                    updateSettings({ showFingeringOnNotes: !settings.showFingeringOnNotes })
+                  }
+                />
+              </Row>
+            )}
+
             <Row
               label="Measure numbers"
               sublabel="on the left edge of falling notes"
diff --git a/frontend/src/engine/AudioEngine.ts b/frontend/src/engine/AudioEngine.ts
index a4befc6..50a5eca 100644
--- a/frontend/src/engine/AudioEngine.ts
+++ b/frontend/src/engine/AudioEngine.ts
@@ -4,18 +4,18 @@ import type { NoteEvent } from "@bach-to-basics/shared";
 // ── Instrument catalogue ──────────────────────────────────────────────────────
 
 export type InstrumentId =
-  | "grand"        // Splendid Grand Piano (SplendidGrandPiano)
-  | "bright"       // Bright Acoustic Piano (Soundfont)
-  | "electric"     // CP80 Electric Grand (ElectricPiano)
-  | "harpsichord"  // Harpsichord (Soundfont)
-  | "honkytonk";   // Honky-Tonk Piano (Soundfont)
+  | "grand" // Splendid Grand Piano (SplendidGrandPiano)
+  | "bright" // Bright Acoustic Piano (Soundfont)
+  | "electric" // CP80 Electric Grand (ElectricPiano)
+  | "harpsichord" // Harpsichord (Soundfont)
+  | "honkytonk"; // Honky-Tonk Piano (Soundfont)
 
 export const INSTRUMENT_LABELS: Record<InstrumentId, string> = {
-  grand:       "Grand",
-  bright:      "Bright",
-  electric:    "E-Piano",
+  grand: "Grand",
+  bright: "Bright",
+  electric: "E-Piano",
   harpsichord: "Harpsi",
-  honkytonk:   "Honky",
+  honkytonk: "Honky",
 };
 
 // Minimal common interface shared by all smplr players
@@ -54,10 +54,20 @@ export class AudioEngine {
     if (this._loaded) return;
     if (this._loadPromise) return this._loadPromise;
     this._loadPromise = (async () => {
-      if (!this.ctx) this.ctx = new AudioContext();
-      this.player = createPlayer(this._currentId, this.ctx);
-      await this.player.load;
-      this._loaded = true;
+      try {
+        if (!this.ctx) this.ctx = new AudioContext();
+        this.player = createPlayer(this._currentId, this.ctx);
+        await this.player.load;
+        this._loaded = true;
+      } catch (err) {
+        // Reset the cached promise so the next call can retry. Without this,
+        // a one-time failure (CDN hiccup, blocked sample fetch, etc.) would
+        // leave _loaded=false and ALL audio permanently silent.
+        this._loadPromise = null;
+        this.player = null;
+        console.error("AudioEngine.load failed:", err);
+        throw err;
+      }
     })();
     return this._loadPromise;
   }
@@ -72,7 +82,11 @@ export class AudioEngine {
     this._loaded = false;
     this._loadPromise = null;
     // Silence any ongoing audio before swapping the player
-    try { this.player?.stop?.(); } catch { /* ignore */ }
+    try {
+      this.player?.stop?.();
+    } catch {
+      /* ignore */
+    }
     this.player = null;
     // Pre-load the new instrument if an AudioContext already exists
     if (this.ctx) await this.load();
@@ -82,6 +96,25 @@ export class AudioEngine {
     return this._loaded;
   }
 
+  /**
+   * Resume the AudioContext after a user gesture. Safe to call repeatedly.
+   *
+   * Browsers' autoplay policy keeps a freshly-created AudioContext in
+   * "suspended" state until a real user gesture. Our `load()` is invoked on
+   * mount (before any gesture) so the context exists but produces no sound
+   * until this is called from a click/keydown handler.
+   */
+  async wake() {
+    if (!this.ctx) this.ctx = new AudioContext();
+    if (this.ctx.state === "suspended") {
+      try {
+        await this.ctx.resume();
+      } catch {
+        /* ignore */
+      }
+    }
+  }
+
   playNote(note: NoteEvent) {
     if (!this.player || !this._loaded) return;
     // Resume in case the AudioContext was created before a user gesture (browser
@@ -104,6 +137,10 @@ export class AudioEngine {
   }
 
   stopAll() {
-    try { this.player?.stop?.(); } catch { /* ignore */ }
+    try {
+      this.player?.stop?.();
+    } catch {
+      /* ignore */
+    }
   }
 }
diff --git a/frontend/src/engine/SyncEngine.ts b/frontend/src/engine/SyncEngine.ts
index 8db7aba..92253b5 100644
--- a/frontend/src/engine/SyncEngine.ts
+++ b/frontend/src/engine/SyncEngine.ts
@@ -11,10 +11,10 @@ interface YTPlayer {
 }
 
 interface SpeedTrainerOpts {
-  enabled:    boolean;
-  startPct:   number;
-  endPct:     number;
-  stepPct:    number;
+  enabled: boolean;
+  startPct: number;
+  endPct: number;
+  stepPct: number;
   currentPct: number;
 }
 
@@ -77,7 +77,11 @@ class SyncEngine {
   private countInBars: 0 | 1 | 2 = 0;
   private countInTimeouts: ReturnType<typeof setTimeout>[] = [];
   private speedTrainer: SpeedTrainerOpts = {
-    enabled: false, startPct: 60, endPct: 100, stepPct: 5, currentPct: 60,
+    enabled: false,
+    startPct: 60,
+    endPct: 100,
+    stepPct: 5,
+    currentPct: 60,
   };
 
   constructor() {
@@ -96,6 +100,39 @@ class SyncEngine {
     this.emitState("stopped");
   }
 
+  /**
+   * Resume both audio contexts (Tone.js + smplr) after a user gesture.
+   *
+   * Required because browser autoplay policy keeps freshly-created
+   * AudioContexts suspended until a real gesture. Our pre-warm in
+   * PracticeView creates them on mount (before any gesture), so without
+   * this they never produce sound. Call from a click/keydown handler.
+   */
+  async wakeAudio() {
+    try {
+      await Tone.start(); // unblock Tone.js context
+      await this.audio.wake(); // unblock smplr context
+    } catch (err) {
+      console.error("SyncEngine.wakeAudio failed:", err);
+    }
+  }
+
+  /**
+   * Swap the document's `notes` array WITHOUT resetting playback state.
+   *
+   * Used to splice in fingering annotations mid-playback. The new array MUST
+   * have the same length, order, and `id`s as the existing one - otherwise
+   * `noteIndex` and `activeNotes` would point at stale data.
+   *
+   * Caveat: notes already scheduled into Tone.js (within ~LOOKAHEAD_DOC_SECONDS
+   * of the current position) keep their old `finger` value via closure capture.
+   * Notes beyond that window are scheduled fresh on the next tick.
+   */
+  updateDocumentNotes(notes: NoteEvent[]) {
+    if (!this.doc) return;
+    this.doc = { ...this.doc, notes };
+  }
+
   async play(fromSeconds?: number) {
     if (!this.doc) return;
     await this.audio.load();
@@ -125,7 +162,7 @@ class SyncEngine {
     const timeSig = this.doc!.timeSignatures[0] ?? { numerator: 4, denominator: 4 };
     const beatsPerBar = timeSig.numerator;
     // Beat duration respects current tempo multiplier so count-in matches playback speed
-    const beatDurMs = (60 / bpm) / this._state.tempoMultiplier * 1000;
+    const beatDurMs = (60 / bpm / this._state.tempoMultiplier) * 1000;
     const totalBeats = this.countInBars * beatsPerBar;
 
     // Ensure metronome synth exists
@@ -143,8 +180,11 @@ class SyncEngine {
     for (let b = 0; b < totalBeats; b++) {
       const isAccent = b % beatsPerBar === 0;
       const id = setTimeout(() => {
-        try { this.metronome!.triggerAttackRelease(isAccent ? "C6" : "G5", "32n"); }
-        catch { /* AudioContext not ready */ }
+        try {
+          this.metronome!.triggerAttackRelease(isAccent ? "C6" : "G5", "32n");
+        } catch {
+          /* AudioContext not ready */
+        }
       }, b * beatDurMs);
       this.countInTimeouts.push(id);
     }
@@ -274,7 +314,10 @@ class SyncEngine {
   }
 
   setHandVolume(vol: { left: number; right: number }) {
-    this._state.handVolume = { left: Math.max(0, Math.min(1, vol.left)), right: Math.max(0, Math.min(1, vol.right)) };
+    this._state.handVolume = {
+      left: Math.max(0, Math.min(1, vol.left)),
+      right: Math.max(0, Math.min(1, vol.right)),
+    };
   }
 
   setWaitForHand(hand: "left" | "right" | "both") {
@@ -285,7 +328,9 @@ class SyncEngine {
     await this.audio.setInstrument(id);
   }
 
-  setYouTubePlayer(player: YTPlayer | null) { this.ytPlayer = player; }
+  setYouTubePlayer(player: YTPlayer | null) {
+    this.ytPlayer = player;
+  }
 
   // ── Practice feature setters ────────────────────────────────────────────────
 
@@ -351,7 +396,9 @@ class SyncEngine {
     return () => this.stateListeners.delete(cb);
   }
 
-  get state(): Readonly<SyncEngineState> { return this._state; }
+  get state(): Readonly<SyncEngineState> {
+    return this._state;
+  }
 
   // ── Private ─────────────────────────────────────────────────────────────────
 
@@ -407,7 +454,11 @@ class SyncEngine {
       const beat = Math.floor(docSeconds / (60 / bpm));
       if (beat !== this.lastBeatCrossed) {
         this.lastBeatCrossed = beat;
-        try { this.metronome.triggerAttackRelease("C6", "64n"); } catch { /* ignore */ }
+        try {
+          this.metronome.triggerAttackRelease("C6", "64n");
+        } catch {
+          /* ignore */
+        }
       }
     }
 
@@ -443,7 +494,10 @@ class SyncEngine {
 
       // note.startSeconds is in doc-time; compare directly to docSeconds
       if (note.startSeconds > docSeconds + LOOKAHEAD_DOC_SECONDS) break;
-      if (this.activeNotes.has(note.id)) { this.noteIndex++; continue; }
+      if (this.activeNotes.has(note.id)) {
+        this.noteIndex++;
+        continue;
+      }
 
       // Apply transposition (creates a new NoteEvent if needed, preserves original id)
       const tNote = this.transposeNote(note);
@@ -454,21 +508,27 @@ class SyncEngine {
       // Convert doc-time offset to real-time for Tone.js scheduling.
       // renderOffsetMs > 0 means audio plays earlier (compensates for delayed output).
       const offsetSec = this.renderOffsetMs / 1000;
-      const onDelay  = Math.max(0, (note.startSeconds - docSeconds) / tempoMultiplier - offsetSec);
-      const offDelay = Math.max(0, (note.endSeconds   - docSeconds) / tempoMultiplier - offsetSec);
+      const onDelay = Math.max(0, (note.startSeconds - docSeconds) / tempoMultiplier - offsetSec);
+      const offDelay = Math.max(0, (note.endSeconds - docSeconds) / tempoMultiplier - offsetSec);
 
       Tone.getTransport().scheduleOnce(() => {
         // Read activeHands at fire-time so hand toggles take effect immediately
         // (not at schedule-time, which would lag up to LOOKAHEAD_DOC_SECONDS).
-        const isActive = note.hand === "unknown" || this._state.activeHands.has(note.hand as "left" | "right");
+        const isActive =
+          note.hand === "unknown" || this._state.activeHands.has(note.hand as "left" | "right");
         if (isActive) {
           bus.emit("note:on", tNote);
           // Apply per-hand volume multiplier (also read at fire-time for instant effect)
-          const handVol = note.hand === "left"  ? this._state.handVolume.left
-                        : note.hand === "right" ? this._state.handVolume.right
-                        : 1;
-          const scaledNote = handVol === 1 ? tNote
-            : { ...tNote, velocity: Math.max(1, Math.round(tNote.velocity * handVol)) };
+          const handVol =
+            note.hand === "left"
+              ? this._state.handVolume.left
+              : note.hand === "right"
+                ? this._state.handVolume.right
+                : 1;
+          const scaledNote =
+            handVol === 1
+              ? tNote
+              : { ...tNote, velocity: Math.max(1, Math.round(tNote.velocity * handVol)) };
           this.audio.playNote(scaledNote);
         }
       }, `+${onDelay}`);
@@ -480,11 +540,13 @@ class SyncEngine {
 
       // Wait mode
       if (this._state.waitMode && this._state.status === "playing") {
-        const isActive = note.hand === "unknown" || this._state.activeHands.has(note.hand as "left" | "right");
+        const isActive =
+          note.hand === "unknown" || this._state.activeHands.has(note.hand as "left" | "right");
         // Only pause for the targeted hand (waitForHand); "both" = current behavior
-        const isWaited = this._state.waitForHand === "both"
-          || note.hand === "unknown"
-          || note.hand === this._state.waitForHand;
+        const isWaited =
+          this._state.waitForHand === "both" ||
+          note.hand === "unknown" ||
+          note.hand === this._state.waitForHand;
         if (isActive && isWaited && onDelay <= 0.05) {
           this.clock.pause();
           this._state.status = "waiting";
@@ -503,7 +565,9 @@ class SyncEngine {
         if (Math.abs(actual - expectedYtTime) > YT_DRIFT_THRESHOLD) {
           this.ytPlayer.seekTo(expectedYtTime, true);
         }
-      } catch { /* not ready yet */ }
+      } catch {
+        /* not ready yet */
+      }
     }
   }
 
diff --git a/frontend/src/store/useAppStore.ts b/frontend/src/store/useAppStore.ts
index 0770976..70b56e4 100644
--- a/frontend/src/store/useAppStore.ts
+++ b/frontend/src/store/useAppStore.ts
@@ -1,7 +1,7 @@
 import { create } from "zustand";
 import { syncEngine } from "../engine/SyncEngine";
 import bus from "../engine/EventBus";
-import type { MusicDocument, PlaybackStatus } from "@bach-to-basics/shared";
+import type { MusicDocument, PlaybackStatus, NoteEvent, Finger } from "@bach-to-basics/shared";
 import type { InstrumentId } from "../engine/AudioEngine";
 export { computeMeasureSeconds, keySignatureToLabel } from "@bach-to-basics/shared";
 export type { InstrumentId } from "../engine/AudioEngine";
@@ -28,17 +28,17 @@ export type ColorTheme = "violet" | "classic" | "ocean" | "forest" | "cascade" |
 
 /** Per-channel colors for the custom theme (hex strings, e.g. "#3b82f6"). */
 export interface CustomColors {
-  leftHand:  string;
+  leftHand: string;
   rightHand: string;
-  unknown:   string;
+  unknown: string;
 }
 
 /** Pre-built color values matching each named preset (used to seed the custom picker). */
 export const COLOR_PRESET_VALUES: Record<Exclude<ColorTheme, "custom">, CustomColors> = {
-  violet:  { leftHand: "#7c3aed", rightHand: "#f59e0b", unknown: "#a78bfa" }, // purple + amber
+  violet: { leftHand: "#7c3aed", rightHand: "#f59e0b", unknown: "#a78bfa" }, // purple + amber
   classic: { leftHand: "#2563eb", rightHand: "#dc2626", unknown: "#7c3aed" }, // blue + red
-  ocean:   { leftHand: "#0284c7", rightHand: "#f97316", unknown: "#0ea5e9" }, // blue + coral
-  forest:  { leftHand: "#16a34a", rightHand: "#a855f7", unknown: "#4ade80" }, // green + purple
+  ocean: { leftHand: "#0284c7", rightHand: "#f97316", unknown: "#0ea5e9" }, // blue + coral
+  forest: { leftHand: "#16a34a", rightHand: "#a855f7", unknown: "#4ade80" }, // green + purple
   cascade: { leftHand: "#9333ea", rightHand: "#22d3ee", unknown: "#a855f7" }, // purple + cyan
 };
 
@@ -46,15 +46,17 @@ export const COLOR_PRESET_VALUES: Record<Exclude<ColorTheme, "custom">, CustomCo
 export type NoteLabelMode = "none" | "c_only" | "white" | "black" | "all";
 
 export interface SpeedTrainerSettings {
-  enabled:    boolean;
-  startPct:   number;   // 0-100
-  endPct:     number;   // 0-100
-  stepPct:    number;   // increment per loop
-  currentPct: number;   // current ramp position
+  enabled: boolean;
+  startPct: number; // 0-100
+  endPct: number; // 0-100
+  stepPct: number; // increment per loop
+  currentPct: number; // current ramp position
 }
 
 export interface AppSettings {
   showFingering: boolean;
+  /** Also overlay finger digits on falling-note bars (default off - adds visual clutter) */
+  showFingeringOnNotes: boolean;
   showHandColors: boolean;
   useFlats: boolean;
   viewportSeconds: number; // FallingNotes lookahead window
@@ -68,49 +70,51 @@ export interface AppSettings {
   metronomeEnabled: boolean;
   // ── New settings ──────────────────────────────────────────────────────────
   /** Note labels on the piano keyboard */
-  noteLabelMode:            NoteLabelMode;
+  noteLabelMode: NoteLabelMode;
   /** Note labels on the falling notes bars */
-  fallingNotesLabelMode:    NoteLabelMode;
-  pianoTheme:          "white" | "ivory";
-  showGrid:            boolean;
-  showMeasureNums:     boolean;
-  showKeySignature:    boolean;
-  transposeSemitones:  number;  // -6..+6
-  speedTrainer:        SpeedTrainerSettings;
-  countInBars:         0 | 1 | 2;
+  fallingNotesLabelMode: NoteLabelMode;
+  pianoTheme: "white" | "ivory";
+  showGrid: boolean;
+  showMeasureNums: boolean;
+  showKeySignature: boolean;
+  transposeSemitones: number; // -6..+6
+  speedTrainer: SpeedTrainerSettings;
+  countInBars: 0 | 1 | 2;
   /** Which visual effect plays when a note reaches the hit line */
-  impactStyle:         ImpactStyle;
+  impactStyle: ImpactStyle;
   sheetMusicWhiteBackground: boolean;
   // ── MIDIano-inspired additions ────────────────────────────────────────────
   /** Scroll wheel on the falling notes canvas seeks playback position */
-  scrollToSeek:        boolean;
+  scrollToSeek: boolean;
   /** Minimum pixel height for note bars (prevents staccato notes becoming invisible) */
-  minNoteHeight:       number;   // 4-24
+  minNoteHeight: number; // 4-24
   /** Border-radius for note bar corners (0 = sharp, 12 = pill) */
-  noteCornerRadius:    number;   // 0-12
+  noteCornerRadius: number; // 0-12
   /** Draw faint horizontal lines at each beat and measure boundary */
-  showBeatLines:       boolean;
+  showBeatLines: boolean;
   /** Show sustain pedal (CC64) regions as semi-transparent bands */
-  showSustainPedal:    boolean;
+  showSustainPedal: boolean;
   /** Per-hand volume multiplier (0 = silent, 1 = full) */
-  handVolume:          { left: number; right: number };
+  handVolume: { left: number; right: number };
   /** Active instrument for audio playback */
-  instrument:          InstrumentId;
+  instrument: InstrumentId;
   /** Which hand(s) trigger wait-mode pauses ("both" = default, all hands) */
-  waitForHand:         "left" | "right" | "both";
+  waitForHand: "left" | "right" | "both";
   /** Draw a colored outline stroke around falling note bars */
-  showNoteOutline:     boolean;
+  showNoteOutline: boolean;
   // ── MIDIano live-app additions ────────────────────────────────────────────
   /** Shift audio scheduling by ±ms to compensate for audio interface latency (positive = play earlier) */
-  renderOffset:        number;   // -200..+200 ms
+  renderOffset: number; // -200..+200 ms
   /** Keep a ghost indicator for notes that have ended while sustain pedal is held */
-  showSustainedNotes:  boolean;
+  showSustainedNotes: boolean;
 }
 
 export interface AppState {
   // ── Document ─────────────────────────────────────────────────────────────
   document: MusicDocument | null;
   isLoadingDocument: boolean;
+  /** True while /fingering/generate is in flight */
+  isGeneratingFingering: boolean;
   loadError: string | null;
   /** Non-null during slow imports (e.g. OMR) to show a descriptive message */
   loadingMessage: string | null;
@@ -134,6 +138,7 @@ export interface AppState {
   loadMidiFile: (file: File) => Promise<void>;
   loadMusicXmlFile: (file: File) => Promise<void>;
   loadPdfFile: (file: File) => Promise<void>;
+  generateFingering: () => Promise<void>;
   play: () => void;
   pause: () => void;
   stop: () => void;
@@ -152,6 +157,7 @@ export interface AppState {
 
 export const DEFAULT_SETTINGS: AppSettings = {
   showFingering: false,
+  showFingeringOnNotes: false,
   showHandColors: true,
   useFlats: false,
   viewportSeconds: 4.0,
@@ -164,31 +170,31 @@ export const DEFAULT_SETTINGS: AppSettings = {
   layoutMode: "falling",
   metronomeEnabled: false,
   // ── New defaults ──────────────────────────────────────────────────────────
-  noteLabelMode:            "c_only",
-  fallingNotesLabelMode:    "all",
-  pianoTheme:          "white",
-  showGrid:            false,
-  showMeasureNums:     true,
-  showKeySignature:    true,
-  transposeSemitones:  0,
+  noteLabelMode: "c_only",
+  fallingNotesLabelMode: "all",
+  pianoTheme: "white",
+  showGrid: false,
+  showMeasureNums: true,
+  showKeySignature: true,
+  transposeSemitones: 0,
   speedTrainer: { enabled: false, startPct: 60, endPct: 100, stepPct: 5, currentPct: 60 },
-  countInBars:         0,
-  impactStyle:         "bloom" as ImpactStyle,
+  countInBars: 0,
+  impactStyle: "bloom" as ImpactStyle,
   sheetMusicWhiteBackground: false,
   // ── MIDIano-inspired additions ────────────────────────────────────────────
-  scrollToSeek:        false,
-  minNoteHeight:       8,
-  noteCornerRadius:    4,
-  showBeatLines:       false,
-  showSustainPedal:    false,
-  handVolume:          { left: 1, right: 1 },
+  scrollToSeek: false,
+  minNoteHeight: 8,
+  noteCornerRadius: 4,
+  showBeatLines: false,
+  showSustainPedal: false,
+  handVolume: { left: 1, right: 1 },
   // ── "Consider later" additions ────────────────────────────────────────────
-  instrument:          "grand" as InstrumentId,
-  waitForHand:         "both" as "left" | "right" | "both",
-  showNoteOutline:     false,
+  instrument: "grand" as InstrumentId,
+  waitForHand: "both" as "left" | "right" | "both",
+  showNoteOutline: false,
   // ── MIDIano live-app additions ────────────────────────────────────────────
-  renderOffset:        0,
-  showSustainedNotes:  false,
+  renderOffset: 0,
+  showSustainedNotes: false,
 };
 
 export const useAppStore = create<AppState>((set, get) => {
@@ -218,6 +224,7 @@ export const useAppStore = create<AppState>((set, get) => {
   return {
     document: null,
     isLoadingDocument: false,
+    isGeneratingFingering: false,
     loadError: null,
     loadingMessage: null,
     status: "stopped",
@@ -280,7 +287,8 @@ export const useAppStore = create<AppState>((set, get) => {
 
         // Stub document - sheet music renders immediately via musicXml string
         const doc: import("@bach-to-basics/shared").MusicDocument = {
-          id, title,
+          id,
+          title,
           sourceType: "musicxml",
           musicXml,
           midiBuffer: null,
@@ -303,9 +311,10 @@ export const useAppStore = create<AppState>((set, get) => {
         // to UTF-8) with a .xml extension, so the backend gets clean MusicXML rather
         // than the ZIP container. This avoids cross-staff voice-duplication artefacts
         // that music21 can produce when it parses a compressed .mxl directly.
-        const xmlBytesForBackend = (musicXml && file.name.toLowerCase().endsWith(".mxl"))
-          ? new TextEncoder().encode(musicXml).buffer
-          : xmlBytes;
+        const xmlBytesForBackend =
+          musicXml && file.name.toLowerCase().endsWith(".mxl")
+            ? new TextEncoder().encode(musicXml).buffer
+            : xmlBytes;
         const filenameForBackend = file.name.toLowerCase().endsWith(".mxl")
           ? file.name.replace(/\.mxl$/i, ".xml")
           : file.name;
@@ -323,7 +332,11 @@ export const useAppStore = create<AppState>((set, get) => {
       const rawTitle = file.name.replace(/\.pdf$/i, "");
       const title = rawTitle.replace(/[\x00-\x1f\x7f/\\]/g, "").slice(0, 200) || "Untitled";
 
-      set({ isLoadingDocument: true, loadingMessage: "Reading sheet music\u2026", loadError: null });
+      set({
+        isLoadingDocument: true,
+        loadingMessage: "Reading sheet music\u2026",
+        loadError: null,
+      });
 
       try {
         const form = new FormData();
@@ -334,11 +347,11 @@ export const useAppStore = create<AppState>((set, get) => {
         const res = await fetch("/api/omr/pdf2midi", { method: "POST", body: form });
 
         if (!res.ok) {
-          const body = await res.json().catch(() => ({})) as { detail?: string };
+          const body = (await res.json().catch(() => ({}))) as { detail?: string };
           throw new Error(body.detail ?? `Server error ${res.status}`);
         }
 
-        const { musicxml, midi_b64 } = await res.json() as {
+        const { musicxml, midi_b64 } = (await res.json()) as {
           musicxml: string;
           midi_b64: string;
           filename: string;
@@ -361,7 +374,6 @@ export const useAppStore = create<AppState>((set, get) => {
 
         set({ document: { ...doc, midiBuffer: bufferForDoc } });
         await syncEngine.loadDocument({ ...doc, midiBuffer: bufferForDoc });
-
       } catch (err) {
         set({ loadError: String(err) });
       } finally {
@@ -369,6 +381,52 @@ export const useAppStore = create<AppState>((set, get) => {
       }
     },
 
+    generateFingering: async () => {
+      const { document: doc } = get();
+      if (!doc?.musicXml) return;
+
+      set({ isGeneratingFingering: true, loadError: null });
+      try {
+        const res = await fetch("/api/fingering/generate", {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ musicxml: doc.musicXml }),
+        });
+        if (!res.ok) {
+          const body = (await res.json().catch(() => ({}))) as { detail?: string };
+          throw new Error(body.detail ?? `Server error ${res.status}`);
+        }
+        const { musicxml: annotatedXml } = (await res.json()) as { musicxml: string };
+
+        const updatedNotes = applyFingeringFromXml(doc.notes, annotatedXml);
+
+        // Guard: don't overwrite if the user loaded a different document while we waited
+        const { document: currentDoc } = get();
+        if (currentDoc?.id === doc.id) {
+          // Note: we deliberately do NOT replace `musicXml` with the annotated
+          // version - fingerings are a piano-keyboard-only overlay.
+          const updatedDoc = {
+            ...currentDoc,
+            notes: updatedNotes,
+            fingeringVersion: "auto" as const,
+          };
+          set((s) => ({
+            document: updatedDoc,
+            settings: { ...s.settings, showFingering: true },
+          }));
+          // Hand SyncEngine the updated notes WITHOUT resetting playback -
+          // notes already scheduled within the lookahead window keep their
+          // old (no-finger) values, but everything beyond it picks up the
+          // new fingerings. This lets the user keep playing through Generate.
+          syncEngine.updateDocumentNotes(updatedNotes);
+        }
+      } catch (err) {
+        set({ loadError: String(err) });
+      } finally {
+        set({ isGeneratingFingering: false });
+      }
+    },
+
     play: () => {
       const { settings, status } = get();
       // Speed trainer: seed the engine's current state before play
@@ -472,11 +530,7 @@ export const useAppStore = create<AppState>((set, get) => {
 
 // ── Helpers ──────────────────────────────────────────────────────────────────
 
-function parseMidiInWorker(
-  buffer: ArrayBuffer,
-  id: string,
-  title: string
-): Promise<MusicDocument> {
+function parseMidiInWorker(buffer: ArrayBuffer, id: string, title: string): Promise<MusicDocument> {
   return new Promise((resolve, reject) => {
     const worker = new Worker(new URL("../workers/midi.worker.ts", import.meta.url), {
       type: "module",
@@ -503,6 +557,117 @@ function parseMidiInWorker(
   });
 }
 
+// ── Fingering helpers ─────────────────────────────────────────────────────────
+
+const STEP_TO_SEMITONE: Record<string, number> = {
+  C: 0,
+  D: 2,
+  E: 4,
+  F: 5,
+  G: 7,
+  A: 9,
+  B: 11,
+};
+
+function xmlStepToMidi(step: string, octave: number, alter: number): number {
+  return (octave + 1) * 12 + (STEP_TO_SEMITONE[step] ?? 0) + Math.round(alter);
+}
+
+/**
+ * Parse fingering annotations from an annotated MusicXML string (returned by
+ * /fingering/generate) and splice them into the existing NoteEvent array.
+ *
+ * Strategy: piano scores from music21 typically have ONE <part> with two
+ * <staff> elements (staff 1 = treble = right, staff 2 = bass = left). We
+ * bucket fingerings by per-note <staff>; for parts with no staff info we
+ * fall back to the part's average MIDI pitch (≥60 → right). Then we match
+ * by position index within each hand group: the i-th XML right-hand note
+ * → the i-th NoteEvent whose `hand === "right"`.
+ *
+ * Pianoplayer encodes "anchored" fingers as circled glyphs (①-⑤); we
+ * normalize those to plain digits.
+ */
+const CIRCLED_FINGER_TO_DIGIT: Record<string, string> = {
+  "①": "1",
+  "②": "2",
+  "③": "3",
+  "④": "4",
+  "⑤": "5",
+};
+
+function applyFingeringFromXml(notes: NoteEvent[], annotatedXml: string): NoteEvent[] {
+  const parser = new DOMParser();
+  const xmlDoc = parser.parseFromString(annotatedXml, "application/xml");
+
+  // Collect finger numbers per hand, in document order
+  const fingersByHand: Record<"left" | "right", (Finger | null)[]> = { left: [], right: [] };
+
+  const parts = Array.from(xmlDoc.querySelectorAll("part"));
+  for (const part of parts) {
+    const noteEls = Array.from(part.querySelectorAll("note"));
+
+    // First pass: do these notes carry <staff> info? (typical for piano grand-staff)
+    let hasStaff = false;
+    let pitchSum = 0,
+      pitchCount = 0;
+    for (const el of noteEls) {
+      if (el.querySelector("rest")) continue;
+      if (el.querySelector("staff")) hasStaff = true;
+      const step = el.querySelector("pitch > step")?.textContent ?? "";
+      const octave = Number(el.querySelector("pitch > octave")?.textContent ?? 0);
+      const alter = Number(el.querySelector("pitch > alter")?.textContent ?? 0);
+      if (step) {
+        pitchSum += xmlStepToMidi(step, octave, alter);
+        pitchCount++;
+      }
+    }
+    const fallbackHand: "left" | "right" =
+      (pitchCount > 0 ? pitchSum / pitchCount : 60) >= 60 ? "right" : "left";
+
+    // Second pass: bucket fingerings into the correct hand
+    for (const el of noteEls) {
+      if (el.querySelector("rest")) continue;
+
+      // Determine hand: prefer <staff> (1 = right/treble, 2 = left/bass), else fallback
+      let handKey: "left" | "right" = fallbackHand;
+      if (hasStaff) {
+        const staff = Number(el.querySelector("staff")?.textContent ?? 1);
+        handKey = staff === 2 ? "left" : "right";
+      }
+
+      const fingeringEl =
+        el.querySelector("notations technical fingering") ??
+        el.querySelector("notations fingering");
+      const raw = fingeringEl?.textContent?.trim() ?? "";
+      const normalized = CIRCLED_FINGER_TO_DIGIT[raw] ?? raw;
+      const finger: Finger | null = /^[1-5]$/.test(normalized)
+        ? (Number(normalized) as Finger)
+        : null;
+      fingersByHand[handKey].push(finger);
+    }
+  }
+
+  // Collect per-hand NoteEvent indices (already sorted by startSeconds in the flat array)
+  const idxByHand: Record<"left" | "right" | "unknown", number[]> = {
+    left: [],
+    right: [],
+    unknown: [],
+  };
+  notes.forEach((note, idx) => idxByHand[note.hand].push(idx));
+
+  // Splice in fingerings by index
+  const updated = notes.map((n) => ({ ...n }));
+  for (const hand of ["left", "right"] as const) {
+    const eventIdxs = idxByHand[hand];
+    const fingers = fingersByHand[hand];
+    const count = Math.min(eventIdxs.length, fingers.length);
+    for (let i = 0; i < count; i++) {
+      updated[eventIdxs[i]] = { ...updated[eventIdxs[i]], finger: fingers[i] };
+    }
+  }
+  return updated;
+}
+
 async function fetchMidiFromXml(
   xmlBytes: ArrayBuffer,
   filename: string,
@@ -531,20 +696,19 @@ async function fetchMidiFromXml(
   }
 }
 
-async function fetchMusicXml(
-  buffer: ArrayBuffer,
-  doc: MusicDocument,
-  _id: string
-): Promise<void> {
+async function fetchMusicXml(buffer: ArrayBuffer, doc: MusicDocument, _id: string): Promise<void> {
   const blob = new Blob([buffer], { type: "audio/midi" });
   const form = new FormData();
   form.append("file", blob, "track.mid");
 
   const titleParam = encodeURIComponent(doc.title ?? "");
-  const res = await fetch(`/api/transcribe/midi2musicxml?title=${titleParam}`, { method: "POST", body: form });
+  const res = await fetch(`/api/transcribe/midi2musicxml?title=${titleParam}`, {
+    method: "POST",
+    body: form,
+  });
   if (!res.ok) return;
 
-  const { musicxml } = await res.json() as { musicxml: string };
+  const { musicxml } = (await res.json()) as { musicxml: string };
   doc.musicXml = musicxml;
 
   // Notify sheet view that MusicXML is now available
diff --git a/frontend/src/views/PracticeView.tsx b/frontend/src/views/PracticeView.tsx
index 317bf25..af35ab5 100644
--- a/frontend/src/views/PracticeView.tsx
+++ b/frontend/src/views/PracticeView.tsx
@@ -44,7 +44,9 @@ export function PracticeView() {
     isLoadingDocument,
   } = useAppStore();
 
-  // Pre-warm audio so piano keys respond with minimal latency.
+  // Pre-warm sample loading so piano keys respond with minimal latency.
+  // Sample fetch (CDN) does NOT need a user gesture - just creates an
+  // AudioContext (suspended) and downloads samples in the background.
   useEffect(() => {
     syncEngine.audio.load().catch(() => {});
     const preWarm = () => syncEngine.audio.load().catch(() => {});
@@ -52,6 +54,24 @@ export function PracticeView() {
     return () => document.removeEventListener("pointermove", preWarm);
   }, []);
 
+  // Wake both audio contexts (Tone.js + smplr) on the FIRST real user gesture.
+  // The pre-warm above creates contexts before any gesture, so browser autoplay
+  // policy keeps them suspended. Without this, no sound ever plays.
+  useEffect(() => {
+    let woken = false;
+    const wake = () => {
+      if (woken) return;
+      woken = true;
+      syncEngine.wakeAudio();
+    };
+    window.addEventListener("pointerdown", wake);
+    window.addEventListener("keydown", wake);
+    return () => {
+      window.removeEventListener("pointerdown", wake);
+      window.removeEventListener("keydown", wake);
+    };
+  }, []);
+
   // Apply theme to <html> element
   useEffect(() => {
     document.documentElement.dataset.theme = settings.theme;