This looks great! What would the cpu usage be of a song consisting of tracks of which 3 are sampled instruments?
I don't have an exact figure but I just checked out the frame rate when playing the sample track, which has 3 sampled instruments most of the time, 1 of them has 3 voices (for the chord), it was at 99 constantly. At the very busy section, with 6 sampled instruments + 3 synth instruments, the FPS various from 60-99, but mostly close to 99. You can download the open source demo project from github which comes with the demo track and check it out yourself too :)