Analog monosynth with sequencer and lo-fi drum machine.

Analog synthesizer with primary VCO and secondary digital square oscillator

  • Saw-core VCO with temperature compensation and accurate tracking over 5 octaves.
  • Optional software-controlled tuning to increase stability and accuracy.
  • Sawtooth and square waveforms, with adjustable pulse-width and pulse-width modulation.
  • Waveform mixer.
  • -1 or -2 octaves sub-oscillator with adjustable level.
  • Secondary digital square oscillator (2.5 MHz programmable interval timer) available as a linear FM source, a VCO sync signal, or an additional audio source sent to the mixer along with the VCO.
  • Mixer with external audio input.
  • 12dB/octave multimode filter (LP/BP/HP), with sine-wave self-oscillation.
  • Post-filter overdrive/fuzz circuit.
  • Linear VCA.

Digitally controlled modulation sources

  • 1 main ADSR routable to pitch, pulse-width, cutoff frequency. Segment time: 1ms to 12s.
  • 1 simple 1-parameter envelope (morphing through various stages, including the shape of the main ADSR, and a rigid “GATE” style envelope) routed to VCA.
  • Velocity routed to either cutoff frequency of VCA gain (adjustable level).
  • 1 LFO routable to pitch, pulse-width and cutoff frequency ; with 8 waveforms (triangle, square, ascending and descending ramps, S&H, bernouilli process, piecewise linear random process, noise). Frequency: 0.06 Hz to 100 Hz. Syncable to arpeggiator/sequencer clock.
  • 1 triangle LFO for vibrato and/or growl controlled by the modulation wheel.
  • CV Resolution: 16-bit internal, 12-bit external, 2.45kHz refresh rate.

Arpeggiator and sequencer

  • Arpeggiator with 4 modes (up, down, up&down, random) ; 1 or 2 octaves ; 6 patterns and “acidity” setting adding accents/slides. Latch/hold mode.
  • SH-101-style note sequencer with step by step recording, up to 128 notes. Along with notes, rests, ties, glides and accents can be recorded.
  • Tempo set by internal clock (40-240 BPM) with shuffle, external MIDI clock or external 6/12/24 ppqn trigger.
  • Keyboard transposition of sequence during playback.

Drum machine

  • Algorithmic drum pattern generator using an innovative “pattern sculpting” approach. Drum patterns are “sculpted” with 5 knobs.
  • Drum sounds can be freely triggered from an external sequencer using MIDI channel 10.
  • x0x-style programming from a MIDI keyboard to override the algorithmic pattern generator.
  • Digital sound synthesis of analog-style BD / SD / HH sounds with tone control.
  • Bit-crusher.
  • Audio resolution: 10 MHz, 1-bit (equivalent to 8-bit, 39kHz).


  • 10 pots and 4 switches for hands-on access to synthesis parameters.
  • 10 “software-pots” for editing modulations / arpeggiator / drum machine settings.
  • 3 dedicated navigation buttons (“modulations”, “clock / arpeggiator / keyboard”, “drum machine”).
  • 3 dedicated sequencer buttons (“record”, “play”, “hold / rest”).


Rear panel

  • 2.1mm power connector, requires 7.5V-9V 300mA supply, with center pin positive, outer collar negative.
  • 6.35mm main audio output.
  • 6.35mm external audio input for VCF/VCA.
  • MIDI DIN in/out.

3.5mm jacks on front panel

  • VCO CV in/out (Note: manual VCO calibration is required for accurate 1V/Oct I/O). Impedance: 200kΩ. Scale: 1V/Oct.
  • VCF CV in. Impedance: 200kΩ. Scale: 1V/Oct.
  • VCA CV in. Impedance: 22kΩ. Scale: 5V for full amplitude.
  • PWM CV in. Impedance: 15kΩ. Scale: -5V to 5V.
  • External Audio in. Impedance: 100kΩ. Line level.
  • Gate signal in/out (2V threshold for input, 5V level for output).
  • 24, 12 or 6 ppqn clock signal in/out (2V threshold for input, 5V level for output).
  • Drum machine individual out (inserting a jack in this output removes the drums signal from the main mix). Line level.
  • Global audio out. Line level.


  • Internal power connector for Eurorack modular systems.
  • Shift register extension for additional triggers or CV outputs (work in progress, supported in the next firmware revision).
  • Patch/test points for DAC CV signals.
  • AVR ISP programmer for code development.


  • MIDI in: notes, CC, pitch bend, aftertouch, start/stop/clock. See the implementation chart and CC table.
  • CC control over ADSR, LFO, VCF cutoff and VCO PWM. Some parameters like filter resonance or VCO waveform mix cannot be CC-controlled.
  • Advanced editing of drum sounds by CC.
  • MIDI out modes (non-exclusive): soft-thru, sequencer/arpeggiator, drum machine notes, clock/sync.
  • Firmware update by SysEx.


  • External dimensions: 21x11.5x4.5 cm. PCB dimensions: 198x109mm. Suitable for 3U / 42 HP modular panel.
  • Anushri is an open-source hardware project, with freely available schematics, BOM, board layout files, and firmware source code.

Olivier Gillet, Mutable instruments SARL 2011-2017. Except where otherwise noted, content on this site is licensed under a cc-by-sa 3.0 license.