The SquishBox

Categories: Hardware Prototypes/Non-Commercial products

Submitted by:Bill Peterson

24 May 2023

Elevator Pitch

The SquishBox

An all-in-one performance synthesizer in a stompbox with 4 USB inputs, infinite instrument splits/layering, effects, arpeggiators, MIDI routing, and more.

Product Description

The SquishBox

The SquishBox is a MIDI sound module built around the Raspberry Pi that adds a high-quality sound card, some simple controls to change settings, a little screen to tell you what it's doing, and fits in a cool stompbox-sized case. It runs the versatile, open-source, and free FluidSynth, which lets you choose from the tons of soundfonts available on the internet, so you have access to instruments such as pianos, organs, and guitars that you can play right out of the box, but you can also create your own synths and effects that you can model and tweak. I wrote FluidPatcher, a customizable synthesizer interface, and created a series of lesson videos that teach you how to create complex performance patches that split and/or layer sounds in endless ways on your instrument's keys or controls, activate and control built-in effects, arpeggiate notes, trigger sequences, play MIDI files, send and route MIDI messages, and more. It also leverages the Pi's wifi to provide a browser-based file manager so the user can easily edit patches and upload soundfonts.

How It's Innovative

This project owes a great deal to the people who have and who continue to contribute to FluidSynth. For a specification developed in the 90s for computer game music, soundfonts are surprisingly versatile. You can use soundfont modulators to control the synthesis parameters, and FluidSynth's built-in ability to activate LADSPA effects and route audio per MIDI channel to create effects chains makes it a surprisingly capable all-around synth. What it lacks is a way to quickly change these settings during a performance, which is what the SquishBox's patch interface provides. Instead of needing multiple devices (e.g. laptop, audio interface, MIDI/USB interface) for live MIDI performance, the SquishBox combines everything into one portable, super-customizable device. The bank file format is easy to understand (lesson videos are provided), and the software also has versions for desktop systems (Windows, Mac OS, Linux) so the user can create, edit, and test new patches live.

See MIDI Innovation In Action

Most Inspiring Use Cases

The most inspiring thing about the SquishBox is its potential for customization. An example is a group of San Francisco Conservatory of Music students who contacted me about building them a SquishBox they could connect to a portable, battery-powered, backpack-mounted speaker. They plugged three wireless keytars into it and formed a strolling classical organ trio they dubbed "The Enlightenment". A big part of their reason for forming was to provide a way to play organ music for people in a safe outdoor setting during the COVID-19 pandemic. You can see some of their work in this video: https://youtu.be/Qz8cj-6Ql4s

Expansion Plans

The current hardware version of the SquishBox uses through-hole components, since these are easiest for beginning hobbyists to solder, however certain compromises had to be made. Using some surface-mount components would allow, for example, using a switching voltage regulator so that 5V power could be safely provided to the Pi from a 5V or 9V adapter without needing to dissipate a lot of heat. It would also be prudent to move away from using a third-party audio DAC card and put these components directly on the board to avoid possible supply chain problems. On the software side, plans include adding looping capability, porting some of the underlying interface code to C to improve latency and audio quality, and creating a DAW plugin version of the software so that patches created for the SquishBox can be used in audio recording sessions.


The SquishBox is currently available on the hardware platform Tindie (https://www.tindie.com/products/15120/). Larger-scale production is not out of the question if demand increases, but the SquishBox will always remain a free hardware product - in the sense that units can be purchased, but the source code, hardware specs and schematics, and construction methods will be made freely available and understandable to anyone. The best innovation comes when everyone shares their ideas and creations.