If you like playing with sounds you will love the NoizBox. Listen to the audio clip of it in action. If you want to make your own Seb has provided the schematic, parts list and code for the PIC microcontroller on his site.

“The stripboard ‘touchpad’ on the right of the right panel was added to give some fingertip control over the second modulation source depth and frequency. The top 10 strips are wired across the Mod 2 Off/On switch with 200K resistors in between each strip so as you slide your finger down from the top (or press harder) the Mod 2 switch becomes progressively more closed. The bottom 6 strips are wired across the Mod 2 Frequency potentiometer, again with 200K resistors in between each strip and this time as you slide your finger up from the bottom (or press harder) the frequency gets higher.”