The SquishBox is a MIDI sound module in a stompbox/guitar pedal format. It is made from a Raspberry Pi, snugly tucked into a Hammond 1590BB enclosure. The Pi runs FluidPatcher, an interface/wrapper I wrote for FluidSynth – an open source Soundfont synthesizer. Soundfonts are a sample-based sound format that is widely used and well-documented. Many soundfonts are available for free, and they can be edited/created with software, the best of which is without a doubt Polyphone.

The SquishBox is open-source, and information is presented here so you can understand how it works and construct your own. If you want one ready-made, they are for sale in my Tindie store, and manuals and support are provided for those here as well.



The SquishBox software interface is an implementation of FluidPatcher (designed by Geek Funk Labs) which provides a patch-oriented interface with FluidSynth. Complete SD card images are available above. If setting up software manually – the Raspbian repositories provide an older version of FluidSynth. It’s recommended to build the latest version of FluidSynth 2, which has more useful features and functionality, from source. The devlogs on this site and FluidSynth wiki can help with this.


The current version of the SquishBox uses a 16×2 character LCD and two buttons. Audio output is provided by a PCM5102 DAC. The image gallery below shows the wiring and construction.