You can always have multiple people singing if you don't count that as cheating. If limits are the deciding factor of an instrument's ultimateness, then I raise

You can always have multiple people singing if you don't count that as cheating. If limits are the deciding factor of an instrument's ultimateness, then I raise that a computer with quality sound hardware + hard drives full of real world audio samples + programmable oscilators is the ultimate instrument. Now that I played my role as captain obvious, fuck it, piano is really the best! (No sarcasm)