diff --git a/app/static/js/app.jsx b/app/static/js/app.jsx
index 36e9b5b..256cc4a 100644
--- a/app/static/js/app.jsx
+++ b/app/static/js/app.jsx
@@ -10390,7 +10390,7 @@ const App = () => {
                   // Only play if the note starts inside the Section item bounds and hasn't finished yet
                   if (noteStartMain >= secStart && noteStartMain < secEnd && offsetTime < noteEndMain) {
                     const notePlayEndMain = Math.min(noteEndMain, secEnd);
-                    const program = subTrack.instrumentProgram !== undefined ? subTrack.instrumentProgram : 0;
+                    const program = subTrack.instrumentProgram;
                     var subCh = window.SonicPianoRoll ? window.SonicPianoRoll.getTrackMidiChannel(subTrack, secTracks) : (subTrack.midiChannel !== undefined ? subTrack.midiChannel : (subIdx % 16));
 
                     if (offsetTime < noteStartMain) {
diff --git a/app/static/js/app.precompiled.js b/app/static/js/app.precompiled.js
index e181982..43178a3 100644
--- a/app/static/js/app.precompiled.js
+++ b/app/static/js/app.precompiled.js
@@ -307,7 +307,7 @@ const sections=track.sections||[];if(activeTab==='main'&&sections.length>0){cons
 const subClips=subTrack.clips||[];subClips.forEach(clip=>{if(!clip.buffer)return;const clipStartLocal=clip.startTime||0;const clipDurLocal=clip.buffer.duration/(clip.speed||1.0);const clipStartMain=secStart+clipStartLocal;const clipEndMain=clipStartMain+clipDurLocal;// Only play within the bounds of [secStart, secEnd]
 const activeStart=Math.max(clipStartMain,secStart);const activeEnd=Math.min(clipEndMain,secEnd);if(activeStart<activeEnd&&offsetTime<activeEnd){const source=context.createBufferSource();source.buffer=clip.buffer;source.playbackRate.value=clip.speed||1.0;source.connect(subNode);if(offsetTime<activeStart){const delay=activeStart-offsetTime;const playOffset=activeStart-clipStartMain;const playDuration=activeEnd-activeStart;source.start(context.currentTime+delay,playOffset*(clip.speed||1.0),playDuration);activeSourcesRef.current.push(source);}else{const playOffset=offsetTime-clipStartMain;const playDuration=activeEnd-offsetTime;source.start(context.currentTime,playOffset*(clip.speed||1.0),playDuration);activeSourcesRef.current.push(source);}}});// 2. Play MIDI items in subTrack
 const subMidiItems=subTrack.midiItems||[];if(window.SonicSF&&subMidiItems.length>0){subMidiItems.forEach(item=>{const notes=item.notes||[];notes.forEach(note=>{const noteStartSecLocal=item.startTime+(note.start_beat||0)*secondsPerBeat;const noteDurSec=(note.duration_beats||1)*secondsPerBeat;const noteStartMain=secStart+noteStartSecLocal;const noteEndMain=noteStartMain+noteDurSec;// Only play if the note starts inside the Section item bounds and hasn't finished yet
-if(noteStartMain>=secStart&&noteStartMain<secEnd&&offsetTime<noteEndMain){const notePlayEndMain=Math.min(noteEndMain,secEnd);const program=subTrack.instrumentProgram!==undefined?subTrack.instrumentProgram:0;var subCh=window.SonicPianoRoll?window.SonicPianoRoll.getTrackMidiChannel(subTrack,secTracks):subTrack.midiChannel!==undefined?subTrack.midiChannel:subIdx%16;if(offsetTime<noteStartMain){const delay=noteStartMain-offsetTime;const startTime=context.currentTime+delay;const playDurMs=(notePlayEndMain-noteStartMain)*1000;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,playDurMs,startTime,program,subNode,subCh,subTrack.synth_engine);}else{const remainingDurMs=(notePlayEndMain-offsetTime)*1000;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,remainingDurMs,context.currentTime,program,subNode,subCh,subTrack.synth_engine);}}});});}});});}});};// Solo playback for Local Selection Loop (LOOP_MAKER.md §2.2)
+if(noteStartMain>=secStart&&noteStartMain<secEnd&&offsetTime<noteEndMain){const notePlayEndMain=Math.min(noteEndMain,secEnd);const program=subTrack.instrumentProgram;var subCh=window.SonicPianoRoll?window.SonicPianoRoll.getTrackMidiChannel(subTrack,secTracks):subTrack.midiChannel!==undefined?subTrack.midiChannel:subIdx%16;if(offsetTime<noteStartMain){const delay=noteStartMain-offsetTime;const startTime=context.currentTime+delay;const playDurMs=(notePlayEndMain-noteStartMain)*1000;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,playDurMs,startTime,program,subNode,subCh,subTrack.synth_engine);}else{const remainingDurMs=(notePlayEndMain-offsetTime)*1000;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,remainingDurMs,context.currentTime,program,subNode,subCh,subTrack.synth_engine);}}});});}});});}});};// Solo playback for Local Selection Loop (LOOP_MAKER.md §2.2)
 const startLocalTrackPlayback=(trackId,offsetTime)=>{const context=getAudioContext();const track=tracks.find(t=>t.id===trackId);if(!track)return;const clips=track.clips&&track.clips.length>0?track.clips:track.buffer?[{id:'default',buffer:track.buffer,startTime:track.startTime||0,name:track.name,speed:track.speed||1.0}]:[];// Get or create persistent gain & panner for real-time control
 const gainNode=getOrCreateTrackNode(track,context);const pannerNode=activeTrackNodesRef.current[track.id].pannerNode;clips.forEach(clip=>{if(!clip.buffer)return;const source=context.createBufferSource();source.buffer=clip.buffer;source.playbackRate.value=clip.speed||1.0;source.connect(gainNode);gainNode.connect(pannerNode);const clipStart=clip.startTime||0;const clipDuration=clip.buffer.duration/(clip.speed||1.0);const clipEnd=clipStart+clipDuration;if(offsetTime<clipStart){const delay=clipStart-offsetTime;source.start(context.currentTime+delay,0);activeSourcesRef.current.push(source);}else if(offsetTime<clipEnd){const playOffset=offsetTime-clipStart;source.start(context.currentTime,playOffset*(clip.speed||1.0));activeSourcesRef.current.push(source);}});// MIDI items playback
 const midiItems=track.midiItems||[];if((track.type==='MIDI'||midiItems.length>0)&&window.SonicSF){const bpmVal=parseInt(bpm)||120;const secondsPerBeat=60.0/bpmVal;midiItems.forEach(item=>{const notes=item.notes||[];notes.forEach(note=>{const noteStartSec=item.startTime+(note.start_beat||0)*secondsPerBeat;const noteDurSec=(note.duration_beats||1)*secondsPerBeat;const noteEndSec=noteStartSec+noteDurSec;if(offsetTime<noteEndSec){const durationMs=noteDurSec*1000;const program=track.instrumentProgram!==undefined?track.instrumentProgram:0;if(offsetTime<noteStartSec){const delay=noteStartSec-offsetTime;const startTime=context.currentTime+delay;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,durationMs,startTime,program,gainNode);}else{const remainingDurMs=(noteEndSec-offsetTime)*1000;window.SonicSF.playNote(note.pitch||60,note.velocity||0.8,remainingDurMs,context.currentTime,program,gainNode);}}});});}};const schedulePianoRollMidi=(st,offsetSeconds,notesOverride)=>{if(st.type!=='PIANO_ROLL')return;const context=getAudioContext();const midiNotes=notesOverride||st.notes||[];const bpmVal=parseInt(bpm)||120;const secondsPerBeat=60.0/bpmVal;const startWallTime=context.currentTime;const track=activeTracksRef.current?activeTracksRef.current.find(t=>t.id===st.trackId):null;const destNode=getOrCreateTrackNode(track,context);const instrumentProgram=track?track.instrumentProgram:undefined;const synthEngine=track?track.synth_engine:undefined;var allTracks=activeTracksRef.current||[];var mainCh=window.SonicPianoRoll?window.SonicPianoRoll.getTrackMidiChannel(track,allTracks):track?track.midiChannel:0;// Compute session beat offset from target item
diff --git a/wiki.md b/wiki.md
index 3295036..8cf5c6d 100644
--- a/wiki.md
+++ b/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 09:37] Task: Section sub-track MIDI playback không default program 0
+- **Tóm tắt thay đổi:** Line 10393 `subTrack.instrumentProgram !== undefined ? subTrack.instrumentProgram : 0` → `subTrack.instrumentProgram`. Trước đây khi `instrumentProgram` undefined (section clone), program default 0 → `_playNoteFluid` gọi `program_change(ch, 0)` trên FluidSynth → load program 0 của MAIN session's SoundFont. Fix: undefined program → `_playNoteFluid` dùng oscillator fallback (không load SoundFont).
+- **Các file ảnh hưởng:** `app/static/js/app.jsx`, `app/static/js/app.precompiled.js`
+- **Ghi chú/Test (nếu có):** `npm run build` pass. Play MAIN session → section MIDI items không load SoundFont. User load instrument trong section tab → program set → FluidSynth play đúng.
+---
+
 ### [2026-07-28 08:49] Task: Revert Synth button ẩn — track có thể chứa cả section + MIDI
 - **Tóm tắt thay đổi:** Revert conditional Synth button (815a6fa). Track có section item con VÀ midi item con → Synth vẫn hiển thị. Instrument chỉ áp dụng cho MIDI item, không ảnh hưởng section item (được xử lý bởi data isolation fix trước đó: section clone null hết soundfont fields).
 - **Các file ảnh hưởng:** `app/static/js/app.jsx`, `app/static/js/app.precompiled.js`