In college, the machines in the computer labs had no speakers, but I found out that by logging on the TTY you could make the PC speaker beep at an arbitrary frequency. You could only play one note at a time, though... except if you used several machines. So I wrote a daemon and a script that would take a MID file and dispatch the various voices to all machines in the room (the daemon used NTP to ensure that everyone started at the exact same time).

The sound quality was awful, but the spatial effect was pretty cool because the sound came from everywhere at the same time. I got cool results with Mario, Pokemon, Tetris, but also some of the Goldberg variations or the Art of Fugue... But this was December, so I dug out a few Christmas tune MIDs and set them to play at random intervals until Christmas. As it turns out, a song triggered during a class once: a lot of people thought the sound was coming from their machine and freaked out, and the teacher spent some time trying to figure out from which machine it came before he understood what was going on.

At some later time we found one computer with sound, so we set up a daemon to monitor logins on all the machines in the room and had a GLaDOS-like voice blurb out a personalized greeting to newcomers. Fun times :)