Steppers are an interesting music controller designed for 5-year olds:
As a group, we hoped to make a toy that not only encouraged physical activity, but that also acted a clear and direct musical interface.
Steppers transform walking, dancing, running, and jumping into a unique and dynamic activity, allowing the user to express themselves audibly through their [...]

Art Institute of Chicago student Chris Burke plays the “Interactopus,” an interactive sculpture controlling sound and live video through eight light sensors, an art bus board, and max/msp/gem.

Max 5 is now available for download. A 30-day demo download is available that combines Max & Jitter.
Max is an interactive programming environment for music, audio, and media. Jitter is a set of video, matrix, and 3D graphics objects for Max.
Max is a true cross-platform system compatible with both Mac OS X and Windows XP/Vista.
Max/MSP/Jitter [...]

Jesse Kriss and DJ Axel Foley have put together an interesting collection of Visual Scratch videos:
We capture turntable velocity using Ms. Pinky and fader position using an Ecler Nuo 4. The scratching sound is generated in Max/MSP. Then we scale the control data (turntable and fader) to ±1.0, the range of digital audio signals. The [...]