Pure FM Magic

MOSTRO is a powerful synth with a straightforward FM sound engine. Like a mix between the resilience of a German birch tree and the beauty of the tropical monstera deliciosa; MOSTRO is ideal for deep and exuberant sonic explorations that retain its unique identity in the vast realm of Frequency Modulated sounds.

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Consistent FM synthesis

Hardware FM synthesizers were historically labeled as "very powerful, yet difficult to control" because, unless you had a very deep knowledge of how it worked, tweaking its parameters led to incomprehensible sonic results. MOSTRO is the result of our design process to overcome this limitation and create a straightforward, easy to use, and versatile polyphonic synthesizer. The FM engine of MOSTRO can be continuously transformed to reach new sounds which are not possible with a classic additive/subtractive synthesizer.

  • A four voice polyphonic synthesizer giving each voice its own envelope, LFO and sub oscillator
  • Each voice has a sinusoidal carrier/modulator system where the carrier modulator ratio, modulation index, and feedback can be controlled from the interface
  • Delay unit and glide control
  • Internal memory that can store up to 100 presets
  • MIDI IN, MIDI OUT, USB and CV connectors allow it to be controlled via external hardware
  • One octave keyboard which in Monophonic Mode it can play anything from chromatic to exotic scales, Polyphonic Mode it can play chords in different keys
  • The MOSTRO is housed in a wooden chassis with a painted steel cover

Control Panel

Versatile connectivity for your workflow

  • Balanced audio output (TRS jack)
  • Headphones output
  • MIDI In and Out
  • USB MIDI In and Out
  • Five CV Inputs: Gate, Pitch, and Oscillator controls (Index, Modulation and Feedback)
  • Full MIDI control of all synthesis parameters
  • Connect DAWs, sequencers and MIDI controllers directly via USB
  • Two USB connections (host and device)
  • Firmware updates and preset management via USB

Backpack friendly

MOSTRO is a compact synthesizer perfectly suited for the road. It is shipped with a panel cover that works both as a quick user manual and as a knob protector so you can safely carry it to your gigs.

Top quality components

All of the electronic components of MOSTRO are top of the line quality so it can have a healthy life once you start using it.

  • Cherry MX and Cherry ML buttons, very popular in the keyboard modding community due to their nice tactile response and durability. They can be operated millions of times without any damage.
  • All the knobs have been specially selected to ensure the best sensation, precision and durability.
  • All of the electronic inputs and outputs have been designed and tested for robustness. You won't damage your MOSTRO if, for example, you connect a CV output to one of the synth's outputs by mistake.

Technical Specifications

    Sound Engine
  • Four voice polyphony
  • One LFO and one envelope per voice
  • Operator parameters: modulation index, ratio, feedback
  • LFO modes: sync or freewheel
    Envelope and LFO Routing

    The envelope for each voice can be routed to the modulation index, ratio and feedback. Envelope routes can be set independently for each parameter or in all possible combinations.

    The LFO can be routed to the modulation index, ratio, feedback and also to the carrier (for a vibrato-like effect). LFO routes can be set independently for each parameter or in all possible combinations.


    MOSTRO comes with an integrated delay unit with time, feedback and effect send parameters. There is also a glissando parameter that controls both the polyphony of MOSTRO (poly or mono); and the time of the note slide (in mono mode).


    The on-board keyboard can be configured to play notes or chords. The scales (note mode) and the types of chords (chord mode) can be configured with a button. The keyboard can be transposed by semitones.


    MOSTRO comes with an integrated MIDI looper unit to record sequences either from the internal keyboard or from external MIDI.


    25cm. x 13cm. x 7cm.

    Power Consumption

    DC 9v 1.5 amp.


    Store up to 100 presets and copy them from/to a computer via USB.

  • 5 control voltage (CV) connections: gate, pitch, modulation index, ratio and feedback
  • USB-A: connect a USB MIDI device such as a controller to send and receive MIDI data
  • USB-B: connect to a computer to send and receive MIDI data, or to update the firmware and manage presets
  • MIDI in and MIDI out/through
  • Headphones output
  • TRS balanced audio output
  • Industrial grade knobs and buttons that allow for millions of interactions
  • Hardwood chasis
  • Stainless steel control panel coated with electrostatic paint, silkscreened and laser engraved


Read the manual to learn even more about the MOSTRO.

Firmware updates

We have not published any firmware updates yet. Here, you'll be able to download firmware update packages with bug fixes and new features.


Version 2.0

  • Released on 2019/8/1
  • This is the firmware version currently shipping with all the MOSTROs. No need to update anything yet.