The Velotone was made for Paddy Austin, who organises bicycle-powered parties and club nights where all of the lights and sounds are generated by pedal power.

A magnet attached to the rear wheel passes a reed switch, which sends a pulse to an 8-stage sequencer mounted on the handlebars.
Depending on the speed of the cyclist, the sequencer plays 8 tunable oscillators, and also controls a Coron DS-7 drum machine.

Paddy and Charlie sent me the video - thanks very much! Visit their website:

The project was finished earlier this year, but I was lucky enough to see it in action at a fabulous party/film night last weekend, where these photos were taken: