Adjust the bit depth of all samples in the current instrument to 8, 16, 24 or 32 bits. Useful for shrinking song file size or when preparing to export sample packs as 16- or 24-bit.
Optionally, only change samples whose bit depths are currently higher -- i.e., don't upsample. This avoids increasing file size when some samples in the instrument are already smaller (e.g. 8-bit).