Groovesizer creates hands-on electronic instruments designed to inspire creativity and exploration. We began with DIY, open-source synthesizer and sequencer kits built around the Arduino platform—accessible, hackable tools for makers and musicians alike.

As we grow, we’re expanding beyond the DIY space to offer fully assembled, ready-to-play instruments. While these new devices are not open source, they continue our mission of delivering fun, intuitive, and innovative tools for electronic music creation.

Theremon+

We’ve been hard at work on the successor the Theremon. While the original features a single voice, the Theremon+ adds a second wavetable-based voice with an arpeggiator, and a drum section with various styles and 4 kits. The original was intended as a DIY kit, but the plan is to offer the Theremon+ fully built and at the same price point as the original (around US$130).

Theremon

Theremon is a digital theremin-style instrument and MIDI controller. Like a traditional theremin, Theremon is played without physical contact with one hand controlling pitch, and the other volume. In the place of the two antennas found on a traditional theremin, Theremon features two time of flight sensors that accurately measure the distance of the player’s hands from the instrument.

TB2

With the Quartet firmware, the TB2 is a 4 voice paraphonic wavetable synth shield for the Arduino Due development board. The TB2 features 2 oscillators per voice, an ADSR envelope, LFO, digital filter,  arpeggiator, as well as a 16-step sequencer.

For sound generation, the TB2 makes use of the pair of 12-bit DACs built into the Arduino Due’s 32 bit ARM processor. The TB2 uses an SD card for storing patches and sequences, and it also allows the user to load single cycle waveshapes for the two oscillators and the LFO.

The Attack! firmware turns the TB2 into a 6 voice drum machine with a 32-step sequencer.

RED

The RED is a 16-step MIDI sequencer and granular synth.

It’s a great kit for first-time DIY builders with a low parts count and clear building instructions.

In spite of its straightforward design, the RED features a number of advanced sequencing features such as various bank and pattern playback modes, note entry quantized to preset and user defined scales, 32 memory locations for storing patterns, and MIDI sync in and out.

Multiboard (MB)

The RED’s big brother is the Groovesizer MB.

NOTE: we no longer offer kits for the MB, but all the design and firmware files are available on these pages if you want to attempt building one for yourself.

It can be transformed into a number of different instruments (sequencer, synth, drum machine, or midi controller) thanks to a growing range of firmware options.

Already available are the Alpha (32-step sequencer and 3 voice monosynth), Bravo (4-voice, 8-bit drum machine), Delta (32-step sequencer and granular synth), Golf (32-step, 12-track MIDI drum sequencer), Foxtrot (clip and scene launcher for Abelton Live), along with a template for developing one’s own firmware.

Here’s a jam with a Groovesizer RED synced to a Groovesizer Golf triggering drum sounds on a Zoom MRT-3.

The Groovesizer philosophy is twofold. First, to provide a platform that helps beginners learn about the design and coding of microcontroller-based electronic musical instruments—offering accessible tools that encourage exploration and creativity. Second, to create distinctive instruments—both DIY and fully assembled—that offer a unique voice and feature set, capable of holding their own in the studio or on stage.