[docs]: add details on how to extract bass guitar and how to create bassless backing track #318

Extract bass from a song:

import drumscript as ds

results = ds.extract_stems("song.wav", all_stems=True, verbose=True)
print(f"Bass stem: {results['bass_stem']}")

Or via CLI:

drumscript song.wav --all-stems

This exports all four Demucs stems (drums, bass, vocals, other) individually. The bass file will be saved as <song>_only_bass.wav.

Create a bassless backing track:

import drumscript as ds

results = ds.extract_stems("song.wav", mute=["bass"], verbose=True)
print(f"Bassless track: {results['mix']}")

Or via CLI:

drumscript song.wav --mute bass

This mixes everything except bass into a single file (<song>_no_bass.wav) and also saves the isolated bass stem separately.