I don't want to turn this into an Excel-hacking extravaganza, but a visitor by the name of Andrew has turned DrumPad into a full-fledged drum machine, albeit one that currently supports only one pattern.
I might expand it to handle multiple patterns, and let you arrange the patterns in a song. Pity I can't figure out how to alter the velocity of the wav.
Hey, I'm still impressed. To run this, you'll need the samples and bass.dll from DrumPad. You can grab Andrew's spreadsheet sequencer here. I'm going to have to move this stuff into the music directory once the link hubbub dies down, because it's not really gaming-related anymore.