Fix piano roll quality, drum sounds, add original audio playback, fix speed

Add drum transcription with madmom onset detection + spectral classification

Fix bass in piano roll, upgrade guitar samples, improve bass optimizer

Use direct melodic transcription for piano roll instead of arrangement

Sample-based guitar/bass sounds, filter bass from piano roll, two guitar tabs

Add instrument-specific audio: guitar synth for guitar tab, bass synth for bass tab

Add piano arrangement engine + guitar/bass tab views for Full Song mode

Add playback progress line and note coloring to sheet music

Fix Demucs OOM on HF Spaces and update Full Song description

Add Full Song mode with Demucs source separation

Update loading time estimate and tighten logo key splay

Add sheet music tab with VexFlow notation and PNG download

Initial commit - Mr Octopus piano tutorial app