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The OM-1 Cassette Synthesizer is an analog musical instrument built around the concept that when a continuous tone/note is recorded to tape, its pitch will change as the tape's playback speed is increased or decreased. Individual notes are playable via the 8 buttons (keys), each with a tuning knob directly above it. The volume of the notes can be articulated by using the pressure sensitive volume control - the harder its pressed, the louder the note. A three position switch controls attack/release response of the audio output - Short, Medium, and Long. CV/Gate inputs allow control over the cassette's pitch and volume from a linear (non-quantized) voltage sequencer.

While loosely inspired by instruments like the Mellotron® and Ondes Martenot, the OM-1 has a sound all its own. Because it uses a standard cassette tape as its audio source, the sound creation possibilities are endless. The OM-1 is engineered for experimentation.





1. TUNING KNOBS: Each knob tunes the button/key directly below it. Pitch range is a little over 2.5 octaves.

2. PERFORMANCE BUTTONS/KEYS: Use these to change the pitch of the sound recorded to tape, the same way you would play keys on a keyboard. Tuned with the knob directly above it.

3. FORCE SENSITIVE VOLUME CONTROL: The harder this is pressed, the louder the audio gets. Controls whatever is plugged into the “IN” jack.

4. ATTACK / RELEASE: Increases the attack and release response of theForce Sensitive Volume Control as the knob is turned clockwise.


6. AUDIO INPUT: 3.5mm jack - Connect this to the cassette player’s Headphone output using a mono (TS) 3.5mm cable. You can also plug in any external audio source and control its volume with the Force Sensitive Volume Control or Gate Input.

7. TAPE SPEED OUTPUT: 3.5mm jack - Connect this to the cassette player’s Tape Speed input (silver jack) using a mono (TS) 3.5mm cable.

8. CV INPUT: 3.5mm jack - Control the pitch of the tape’s sound from a linear (non-quantized) CV sequencer, such as the Korg SQ-1 (5V Max).

9. GATE INPUT: 3.5mm jack - Plug in the Gate Output from a CV sequencer to gate the audio being fed into the “IN” jack.

10. POWER SUPPLY INPUT: Use only the 3V center positive wall adapter supplied with the unit in order to avoid any damage to circuitry.

11. AUDIO OUTPUT: 1/4" jack - Plug this into an amplifier, external effects, etc.

12. PITCH RIBBON INPUT: 3.5mm jack - (see DIY instructions below)






• When recording onto a cassette, plug a line level signal into the Mic jack and set REC TIME to “normal”

• Set the input level from your source, as the cassette recorder has no record level control

• When playing the OM-1, set REC TIME to “double”

• Runs on 2 AA batteries (not included)




Onde Magnétique (magnetic wave) is home to the cassette-based electronic musical devices of Scott Campbell. Each piece is hand-built in New Orleans, LA in limited quantities.

Special thanks:
Joshua Edward Bennett
Britt King (video)
Zack Smith (photography)