VOICE selects the default instrument used by generated notes and PLAY strings. In sfxlib, an instrument is a combination of a waveform and an envelope, which together decide the general tone color and how the sound starts and fades.

Changing VOICE is like switching from one simple synth patch to another. A sine-like instrument can sound soft and clean, while a square or saw instrument can sound more electronic or buzzy.

Calling VOICE as a function returns the current default instrument id.