remove dead air

app.py

@@ -25,6 +25,8 @@ def main():
 
     record = dataset[record_idx]
     piece = MidiPiece.from_huggingface(record)
+    piece.time_shift(-piece.df.start.min())
+
     st.json(piece.source)
 
     piece_split = piano_task.prompt_target_split(piece.df)