The Open Theremin is an open source hardware and software project, with the aim is of building a next-generation, DIY theremin.

Two Open Theremin designs are available:

• The Open.Theremin.UNO is a full Arduino-based theremin that offers both audio and control voltage outputs.
• The Open.Theremin.RC is a more basic one-antenna (pitch) design.

The project is documented under a creative commons license.

Open.Theremin.UNO Features:

• Pitch and volume antenna with excellent linearity and digital tuning
• Arduino compatible shield for easy programming
• 12bit digital to analog converter generates audio out signal
• Waveform can be reprogrammed freely (stored in a look-up table)
• Audio plug can be reprogrammed to provide Control Voltage (CV)
• Connector for audio or control voltage on board
• USB powered, no extra power supply required
• Can be powered by battery
• Low profile SMD design for simple shipment
• Pads to screw or solder on antennas or antenna cable
• One button interface
• Distance of hand to antenna is converted to a digital value that can be used for other applications than theremins
• Pads to connect analog potentiometer (or digital encoder)
• Pads to connect grounding directly to board

Here’s a video of the Open.Theremin.Uno in action:

Here’s an example of a DIY Matryomin Matryoshka Doll Theremin, based on the Open Theremin:

Open.Theremin.RC

The Open.Theremin.RC is a simple and basic theremin circuit with one pitch antenna.

The circuit will run on a 9V battery and produce a triangular output signal. The circuit is good to explore the basic theremin principle of heterodyne oscillators.

Kits for both theremin projects are available via the Open Theremin site.