In relation to pac-man's sound (not the siren but the sound he makes when he eats pills) I ran into that when creating my own synthesiser controlled by an xbox controller. I had two sine waves with their pitches doubling every x seconds, controlled by the two thumbsticks. (up would increase and down would decrease their pitches independently). Anyway I found if I held both of the thumbsticks upwards the sine waves would get so high they would overflow the speakers and then keep looping that overflow faster and faster, and it actually sounded like pac-man eating the pills. And thats when I realised it might actually be true, he really might be eating pills and getting that high.