> You say that a trained musician can hear an error of "tens of microseconds." It seems to me that I once heard somewhere, many years ago, that a person can't hear an echo from any object closer than 30 feet. That would be 60 feet round-trip. If the speed of sound is 1100 feet per second, that means the shortest echo a person can hear is 55 milliseconds (55,000 microseconds). So, it seems to me that the note timing needs to be accurate to about 50 milliseconds. It would be interesting to measure the time between drum beats played by a professional drummer, to see how much variance there is in the intervals.