Turi Scandurra's Diapasonix Is a Raspberry Pi Pico 2-Powered Handheld Synth for String Players
3D-printed capacitive touch elements are designed to provide a familiar playing experience for those used to guitars, violins, and more.
Maker and musician Turi Scandurra has shared the first version of a portable, fret-based synth and MIDI controller designed to be familiar to those used to stringed instruments: the Raspberry Pi RP2350-powered Diapasonix.
"Diapasonix is a portable electronic musical instrument and MIDI controller that is played similarly to a stringed instrument," Scandurra explains of his creation. "It features a capacitive touchpad fretboard, I2S audio output, and a built-in synthesizer with chainable audio effects powered by the AMY synthesis engine. Its four-string, six-fret layout (24 touch points total) can be set up to match traditional stringed instruments like guitar, bass, ukulele, violin, double bass, banjo, and so on. If you can play any of these instruments, you can play Diapasonix!"
Inside the machine's compact housing is a Raspberry Pi Pico 2 board, which in turn hosts a Raspberry Pi RP2350 microcontroller. This is linked to a capacitive touchpad split into four "strings" with six frets each. The AMY synthesis engine runs entirely on the microcontroller itself, loaded with 128 Juno-6 patches and 128 DX7 patches — and there's an OLED display panel to let you switch between each while also enabling and disabling reverb, chorus, echo/delay, distortion, and low-pass filter effects.
That's an impressive-enough list of features, especially given the instrument's size, but there's more: the synth includes per-string tuning and capo transposition, can be played as a strummed or tapped instrument, can be flipped into left-hand mode, includes four user preset slots, battery monitoring for its internal rechargeable battery, and the ability to use it as a USB MIDI controller.
"I have not yet put together a step-by-step guide to assemble the Diapasonix," Scandurra says of the current state of the project, the first prototype of which has been built and tested. "I might want to wait until we get to a stable version. I'm changing components and overall design and breaking things as I move. The current capacitive fretboard might undergo a major re-engineering. One note about the v1 design: the frets are 3D-printed, then dipped in conductive silver paint, and finally coated with a single layer of nail polish. They react very well to even the gentlest of touches."
Full source code, design files, 3D-print files, and schematics are available on GitHub under an unspecified license.