I used to write code for a certain machine that ran long, complex sets of instructions. We could tell what sequence it was running by listening to the "tune" th

I used to write code for a certain machine that ran long, complex sets of instructions. We could tell what sequence it was running by listening to the "tune" the motors played as it ran. Was also easy to tell when there was a bug or some other problem: the sound would be "off" and sure enough, a few seconds later there'd be an error message on the display.