refactor piano instrument to use PolySynth for improved sound dynamics and volume control

index.html

@@ -470,17 +470,15 @@
     const reverb = new Tone.Reverb({ decay: 3, wet: 0.25 })
     const delay = new Tone.FeedbackDelay("8n", 0.2).connect(reverb);
 
-    // 3. Nhạc cụ chính: Giảm mạnh Volume gốc
-    const piano = new Tone.Sampler({
-        urls: {
-            "C4": "C4.mp3",
-            "D#4": "Ds4.mp3",
-            "F#4": "Fs4.mp3",
-            "A4": "A4.mp3",
-        },
-        baseUrl: "https://cdn.jsdelivr.net/gh/Tonejs/audio@master/salamander/",
-        release: 1,
-        volume: -6
+    const piano = new Tone.PolySynth(Tone.AMSynth, {
+        volume: -8,
+        harmonicity: 1.5,
+        envelope: {
+            attack: 0.02,
+            decay: 0.3,
+            sustain: 0.3,
+            release: 2
+        }
     }).connect(delay);
 
     piano.triggerAttackRelease(