It’s hard to play, has a limited choice of notes, and sounds like it’s been sitting in a dusty attic for half a century. But the OM-1 Cassette Synthesizer is a quirky beast with an appealing sound that’s all its own. It utilizes continuous tones on a cassette tape and 8 buttons that can change the playback speed in order to create different pitches. Each button can be individually tuned so you can create whatever scales you want, and a pressure sensitive volume control allows you to change the volume by pressing harder or softer. It even includes some basic envelope controls. The maker is currently sold out so you’re going to have to find one on eBay or Reverb. http://www.ondemagnetique.com