"Data Cassette for Korg Poly 61 analog synthesizer with factory MIDI retrofit."
Note the auction states the Korg Poly 61, but the cassette clearly has Poly 6 printed on it. The Polysix wasn't spelled Poly 6. Anyone know more about this?
EVERYTHING SYNTH
Image pulled via this electro-music.com post, where you will find one more image and info via funkyfarm. Title link takes you to the DIY page containing more info on the adaptation along with the following:
- tube distortion**