Johan made a guitar distortion pedal from an old walkman, there are not a ton of details, but looks like it would be fun to build – “..I’ve taken a walkman and converted it to a guitar distortion pedal. This was pretty easy actually, and I got the idea from the net and I wanted to try it out myself. The theory is that you use the amplification part of the walkman to aplificate another signal then the zeros and ones stored on a casette tape.” – Link.