An electrical toothbrush is connected to an audio player. A analog curcuit that is placed where normally the batteries go regulates the rotation of the brush according to the audio gauge. Feeling music.

The curcuit had to be layouted carefully to fit into the battery slot. You can see the result here.

An applet illustrates the project.
The Applet needs the JSyn plugin which can be downloaded here.

The applet can play back audio
or react on microphone input.

For PC: The device selected in 'Control Panel > Sounds and Audio Devices' is used.

For Mac: The current microphone is used.

If you don't want to install JSyn, you can see a simulated version here.