thingstruments

Another Arduino made instrument: the Bleep Drum. See Bleep Labs' store for more info . A kit will cost you $60.

The Ondes Martenot is an old electronic instrument that sounds like the theremin . This guy made his own, modern version of the Martenot, for controlling a Korg Monotribe. Check it out! The post at Hack a Day has some more information for those interested in building their own.

Nice short video interviewing Peter Edwards on circuit bending, what else.

Doesn't get much simpler than this! Just glue a piezo to the kazoo and solder it to an audio jack .

Here's a video demonstrating a breadboard based modular synthesizer by STEIM: This seems like a great way to create a VERY complex modular with minimal effort - no need to have kilograms of patch cables and banana jacks! For more info, see the webpage with documentation . Found from the circuit-bending and musical diy Google+ community .

This guy made some enhancements to his guitar with an Arduino... just awesome!!! Read more on the details at Hack A Day .

This one is really a strange instrument indeed. I'm not sure I fully understand what the sidrazzi even is. Seems to be on the glitch department. Here's a part of the author's description , though it doesn't help much: The Sidrassi is an Organ, designed to reflect the glory of god with pure triangular voices. But it also allows exploration of the Devils' Tone, which is irrational pitch relationships achieved through analog modulations.  And here's the video you're waiting for: