This looks like a really interesting touch screen music synthesizer. They claim to be creating a how-to soon. Check out the link for more information.

Broadly, the purpose of this project was to create an Analogue modeling musical synthesizer;
that is, a synthesizer implemented using both analogue and digital components that intends to emulate the sounds of traditional analogue synthesizers, whilst being controllable through modern-day digital protocols such as the Musical Instrument Digital Interface (MIDI).

More about the DIY synthesizer