fix stereo image when creating medley

mcp_server.py

@@ -748,8 +748,8 @@ def align_songs_by_bpm_mcp(
 def create_medley_mcp(
     vocals_path: str,
     instrumental_path: str,
-    vocals_gain: float = 0.65,
-    instrumental_gain: float = 1.0,
+    vocals_gain: float = 0.6,
+    instrumental_gain: float = 1.2,
     output_format: str = "wav",
 ) -> str:
     """
@@ -762,8 +762,8 @@ def create_medley_mcp(
 
         vocals_path: Path to the vocals audio file or URL (supports common formats: WAV, MP3, FLAC, M4A)
         instrumental_path: Path to the instrumental audio file or URL (supports common formats: WAV, MP3, FLAC, M4A)
-        vocals_gain: Gain multiplier for vocals (default: 0.7, typical range: 0.5-1.0)
-        instrumental_gain: Gain multiplier for instrumental (default: 0.8, typical range: 0.5-1.0)
+        vocals_gain: Gain multiplier for vocals (default: 0.6, typical range: 0.5-1.0)
+        instrumental_gain: Gain multiplier for instrumental (default: 1.2, typical range: 0.5-2.0)
         output_format: Output format for medley ('wav' or 'mp3', default: 'wav')
 
     Returns:
@@ -788,7 +788,7 @@ def create_medley_mcp(
             instrumental_path=instrumental_path,
             vocals_gain=vocals_gain,
             instrumental_gain=instrumental_gain,
-            compressor="threshold=-18dB:ratio=3:attack=50:release=200",
+            compressor="threshold=-12dB:ratio=3:attack=50:release=200",
             audio_codec="libmp3lame" if output_format == "mp3" else "pcm_s16le",
             audio_bitrate="192k" if output_format == "mp3" else "",
             output_path=None,  # Use default temp location
@@ -1456,7 +1456,7 @@ def create_interface() -> gr.TabbedInterface:
                 value=0.6, label="Vocals Gain", minimum=0.1, maximum=3.0, step=0.1
             ),
             gr.Number(
-                value=1.1, label="Instrumental Gain", minimum=0.1, maximum=3.0, step=0.1
+                value=1.2   , label="Instrumental Gain", minimum=0.1, maximum=3.0, step=0.1
             ),
             gr.Dropdown(
                 choices=["wav", "mp3"],

tools/combine_tracks.py

@@ -328,9 +328,10 @@ def create_medley(
         output = Path(output_path).expanduser().resolve()
         output.parent.mkdir(parents=True, exist_ok=True)
 
-    # Enhanced stereo mixing with better channel balance
+    # Enhanced stereo mixing with centered vocals and preserved instrumental stereo
     filter_complex = (
-        f"[0:a]volume={vocals_gain}[v0];"
+        f"[0:a]volume={vocals_gain},"
+        f"pan=stereo|c0=c0|c1=c0[v0];"
         f"[1:a]volume={instrumental_gain}[v1];"
         f"[v0][v1]amix=inputs=2:duration=longest:dropout_transition=2:weights='1.2 0.8',"
         f"acompressor={compressor}"
@@ -451,14 +452,14 @@ if __name__ == "__main__":
     medley_parser.add_argument(
         "--vocals-gain",
         type=float,
-        default=1.2,
-        help="Linear gain for vocals (default: 1.2)",
+        default=0.6,
+        help="Linear gain for vocals (default: 0.6)",
     )
     medley_parser.add_argument(
         "--instrumental-gain",
         type=float,
-        default=0.9,
-        help="Linear gain for instrumental (default: 0.9)",
+        default=1.2,
+        help="Linear gain for instrumental (default: 1.2)",
     )
     medley_parser.add_argument(
         "--compressor",