• Developer Guide

    The OTTO


    The OTTO is an open source digital hardware groovebox, with synths, samplers, effects and a sequencer with an audio looper. The interface is modular, easy to use, simple, but most of all, it encourages experimentation. The graphics are quirky, and the workflow is minimalistic.

    We would like to invite you to our discord server where we hang out and discuss all things OTTO.

    Support the project

    As hardware test boards costs money, and many of you have asked how you can contribute in a financial way, we have decided to set up a Patreon account. With Patreon, you can send us a small monthly amount of money, or make a one-time donation by cancelling the monthly subscription after the first payment (Note that this usually happens on the first of the month, not immediately.)

    All funds go directly towards the OTTO

    Prototype Demo

    This is a demo of an early prototype unit, with only a few features implemented.

    The beta

    We're working on a beta version, aimed for late february 2020. Take a look at the full announcement for more information.

    The hardware

    The OTTO hardware has a Raspberry Pi 3A+ at the core of a custom PCB with the buttons, a screen, 4 encoders, tons of RGB LEDs, and a MCU controlling the I/O. It also contains a DAC for audio I/O.


    Planned Features

    The ones marked will be available in the beta.

    • A synth for live performance with midi effects (arpeggiator, etc.)
    • 2 FX slots. Synths and drums send to them as a FX bus.
    • Synths and effects are swappable "engines".
    • For drums, a sampler will run in parallel to the sequencer-synth chain.
    • The drum sampler has 10 channels. These have a simple 1-bar, 16 step drum sequencer, with each step corresponding to a white key on the keyboard.
    • An audio line input which has FX send and level
    • A simple loop-station-style audio looper that can get audio from line in or synth. It has overdub and one level of Undo.
    • 8 save slots which save the state of the entire system. A save button lets you choose the slot to save in. Saves are only performed when you take the action.


    The UI tries to walk the line between clear, concise and playful:

    otto screenshots