Adding/increasing tracks or instruments might be possible with MIDI. But using MIDI as the final format of the score isn't much of an option anymore these days, is it... A similar effect could be created using modules (.xm, .it and the likes) but the quality of those would never come close to Kirill's needs I'm afraid. It could probably even be done using ogg-files (or mp3 or wavs) but that would not only be quite an efford, it would of course also take up too much memory.
So narrow the idea down... what do you get then? Probably something similar to what Raze was already referring to. I'm kind of hoping they'll be implementing it now for RR and/or D2 <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Doesn't that go back to the LMK age btw?

Mr Kej, Second Member of the Guild of Off-Topic Posters *** Visit Aviorn's Inn, my Divine Divinity fansite ***