Cassettes (if you remember those) are normally used to play back music and other audio, but what about using an old Walkman-style tape player as the instrument itself? That’s exactly what this project by Zack Scholl allows you to do, varying the playback speed to modify pitch output.
It’s a very simple setup, requiring one to hook up wires that enable an Arduino Uno and MCP4725 DAC to adjust the speed using a voltage input. A drone sound is recorded on the tape, which may also involve some hacking depending on your equipment.
The Walkman then emits this recorded sound, which the Arduino — here using a keyboard and computer browser-based MIDI interface — modulates by increasing or decreasing the playback speed.