fix: program_change at call time overrides subsequent notes

_playNoteFluid called program_change synchronously at
call time, not at scheduled note time. startTrackPlayback
processes all MIDI items first, then all sections -> each
note's program_change overwritten by the last type processed.
All notes played with section instrument regardless of
actual time position. Moved program_change into doNote
(setTimeout callback) so it fires at correct time.

app/static/js/services/soundfontPlayer.js

@@ -362,21 +362,40 @@
                 typeof velocity === 'number' ? (velocity > 1 ? velocity : velocity * 127) : 100
             )));
             var _origChannel = channel;
-            var ch = channel;
             var usedBank = 0, usedProg = 0;
             if (synthEngine) {
                 usedBank = synthEngine.soundfont_bank || 0;
                 usedProg = synthEngine.soundfont_program || 0;
-                if (ch === undefined) {
+                if (channel === undefined) {
                     var engKey = (synthEngine.soundfont_id || '') + ':' + usedBank + ':' + usedProg;
                     var mappedCh = _engineChMap[engKey];
                     if (mappedCh !== undefined) {
-                        ch = mappedCh;
+                        channel = mappedCh;
                     } else {
-                        ch = usedBank === 128 ? 9 : 0;
+                        channel = usedBank === 128 ? 9 : 0;
                     }
                 }
-                if (ch === undefined) ch = (usedBank === 128 ? 9 : 0);
+                if (channel === undefined) channel = (usedBank === 128 ? 9 : 0);
+            } else if (program !== undefined) {
+                usedProg = program;
+                if (channel === undefined) channel = 0;
+            } else {
+                // No instrument configured: silent — no FluidSynth, no oscillator.
+                return;
+            }
+            if (channel === undefined) channel = (usedBank === 128 ? 9 : 0);
+            var ch = channel;
+            var ctx = getCtx();
+            var now = ctx.currentTime;
+            var delay = (typeof startTime === 'number' && startTime > now) ? (startTime - now) : 0;
+            var durSec = (durationMs || 500) / 1000;
+            var scheduledNote = { on: null, off: null };
+            var self = this;
+            var doNote = function () {
+                try {
+                    // Program change at note time, not call time — ensures correct
+                    // instrument for each item regardless of processing order.
+                    if (synthEngine) {
                         var sfHandle = synthEngine.soundfont_id ? _sfHandleMap.get(synthEngine.soundfont_id) : undefined;
                         if (sfHandle !== undefined) {
                             try {
@@ -387,24 +406,10 @@
                             try { _fluidModule._fluid_synth_program_change(_synthPtr, ch, usedProg); } catch (e) {}
                         }
                     } else if (program !== undefined) {
-                usedProg = program;
-                if (ch === undefined) ch = 0;
                         try {
                             _fluidModule._fluid_synth_program_change(_synthPtr, ch, usedProg);
                         } catch (e) {}
-            } else {
-                // No instrument configured: silent — no FluidSynth, no oscillator.
-                return;
                     }
-            if (ch === undefined) ch = (usedBank === 128 ? 9 : 0);
-            var ctx = getCtx();
-            var now = ctx.currentTime;
-            var delay = (typeof startTime === 'number' && startTime > now) ? (startTime - now) : 0;
-            var durSec = (durationMs || 500) / 1000;
-            var scheduledNote = { on: null, off: null };
-            var self = this;
-            var doNote = function () {
-                try {
                     console.log("[SonicSF] noteOn ch:", ch, "pitch:", midiPitch, "vel:", midiVel);
                     _fluidModule._fluid_synth_noteon(_synthPtr, ch, midiPitch, midiVel);
                     var noteMapKey = (_origChannel !== undefined ? _origChannel : 0) + ':' + midiPitch;

wiki.md

@@ -539,6 +539,12 @@
 - **Ghi chú/Test (nếu có):** `npm run build` pass. Ctrl+Click+Drag section/MIDI item → copy đến vị trí mới, item không bị selected.
 ---
 
+### [2026-07-28 09:50] Task: Program change ở note time, không phải call time
+- **Tóm tắt thay đổi:** Di chuyển `program_change`/`program_select`/`bank_select` từ synchronous (call time) vào trong `doNote` (note time via setTimeout) trong `_playNoteFluid`. Trước đây tất cả program_changes xảy ra ngay khi `startTrackPlayback` chạy → MIDI items processed trước sections → section's program_change override cuối cùng → ALL notes (section + MIDI) play với section instrument. Fix: mỗi note có program_change tại đúng thời điểm của nó.
+- **Các file ảnh hưởng:** `app/static/js/services/soundfontPlayer.js`
+- **Ghi chú/Test (nếu có):** load. TRACK 1: | SECTION ITEM (inst B) | MIDI ITEM (inst A) | → section plays inst B, MIDI item plays inst A.
+---
+
 ### [2026-07-28 09:30] Task: Thêm _isSectionClone flag — tắt âm thanh mặc định trong SECTION-TAB
 - **Tóm tắt thay đổi:** Thêm `_isSectionClone: true` vào section cloned tracks. Line 10283 kiểm tra flag: nếu section clone và không instrument → `undefined` (silent); nếu MAIN track và không instrument → `0` (GM Piano). Trước đây section cloned tracks đi qua line 10283 với `instrumentProgram: undefined` → default 0 → play GM Piano.
 - **Các file ảnh hưởng:** `app/static/js/app.jsx`, `app/static/js/app.precompiled.js`