I bet the Macintosh II will play AIFF's

but then again that is a 68020, so that's not too exciting for me

university of michigan has a great old mac freeware archive

http://www.umich.edu/~archive/mac/

http://www.umich.edu/~archive/mac/sound/sounds/99bottles.cpt.hqx

this plays on the SE/plus/classic

the computer will sing 99 bottles of beer on the wall and count down.

http://www.umich.edu/~archive/mac/sound/sounds/rapmaster1.01.sit.hqx

this one is rap master, it gives you a record you can scratch and make funky beats