I decided to put to good use the a few of the hundreds of audio cassettes I've seen gathering dust in boxes around local thrift stores. This is the result:
Construction was simple.
I picked up a lower than low-end cassette player from Amazon and tore out the tape head. The head is just a simple transducer and doesn't require any other circuitry. It has literally just two output wires (4 wires for stereo, my player was mono) that produce an unamplified audio signal. I wired the tape head outputs directly to a female 1/4" audio jack, plugged in a guitar cable, and ran it straight to the mic input on my mixer. Then I zip tied and screwed everything in to a 1' piece of scrap wood to form a tape head stylus.
The next step was to create a tape palette to scrub the wand against. I cracked open a dozen thrift store cassette tapes, snipped out random 18" lengths of tape, and stretched ~100 of the strip across a piece of corkboard. I clamped more scrap wood across the edges to hold things tight. The result was about 200 square inches of tape containing random audio that I could tease out by sliding the tape head wand around.
"Playing" the cassette scrubber requires some nuance. Despite the size of the head, the actual point that must make contact with the tape is quite small. If the head doesn't make direct contact with the tape, there's no sound produced. Also, it's close to impossible to move the head at a consistent speed (at least for me) so the sound warbles greatly. But that's part of the charm.
I'll get audio samples and possibly a video up soon.