How to use this demo

1. Upload audio → F₀ is estimated (unvoiced regions are hidden).
2. Edit the target contour:
    • Use the Semitone shift slider to transpose the original curve.
    • Or draw directly on the F₀ plot to create a custom contour.
    • Click Record Drawing to apply it.
    • You can also use the slider to modify a drawn contour.
3. Regenerate the audio to hear the result.