Want to make a Xylophone? Take a look here.

And on a totally unrelated note (argh, pun not intended, but gladly used!), here's some information on making your own MIDI controllers. There's also a nice set of links to various circuits you can build as well. Want to build your own electronic drums? it's totally doable. Or how about a midi controller for an instrument that doesn't have a commercial midi controller? certainly within the realm of possibility. I think a Didgeridoo like instrument hooked up to that weird sound generator board I linked to a bit ago would be seriously cool... hmmmm....