There is nothing like the feeling of performing music for a crowd. There is also nothing like hitting a chord in a big empty space and listening while the sound slowly fades away.

Related to instruments themselves, the trial and error is one very important aspects I can think of right now that's enjoyable: playing something off beat or out of tune and correcting yourself. The feeling of correction and improvement.

It is a real pity the actual algorithm itself has no way to enjoy what it is creating.