Apologies if this has already been suggested (or even implemented)…
Naturally, we can mute / sole channels to isolate sounds. But for channels where you have multiple instruments contained (for example the drums and bass channel), it would handy to be able to listen to just the bass or just the kick, say.
Some way to implement this might be in the instrument list, a mute/solo box next to the colour of the instrument maybe.
Another (fairly wild) feature I thought might be pretty cool would be to mimic side-chain compression using a pattern command. For example, you could use a pattern command along with the kick drum, and then this would automatically lower the volume of all other channels for a time/volume percentage value specified on the command.