Marcus Stephen Edwards' Raspberry Pi-Powered MIDI Controller Cuts a Guitar Down to Size

Scientist, engineer, and maker Marcus Stephen Edwards has built a guitar with a difference: it only has four frets and a head, turning untuned strings into MIDI inputs for a Raspberry Pi 2 Model B single-board computer.

"My instrument building hobby started mostly working with hand tools on the deck in the summertime," Edwards explains by way of introduction to the project. "[This] is a hand-made, custom MIDI controller made from a piece of pine wood, a Raspberry Pi 2 Model B, wearable Adafruit Flora and a[n STMicroelectronics] LSM303 accelerometer module. After building a few traditional guitars and having a lot of fun with the fretless one, I felt inspired to do something new."

In a traditional guitar, strings run from the head to the body along a neck covered in frets; as the string is pressed to shorten its length, the pitch shifts and is amplified inside the guitar's hollow body. Electric guitars typically enjoy the same rough layout, but with a solid body and electric pickups to turn the strings' vibration into audible sound.

Edwards' latest creation, though, looks like someone tried to make a guitar from a badly-cropped image: there's a head, and the first four frets of a neck — and that's it. "There is hardly any length to the MIDI guitar's neck so there is no need to worry about bend or a truss rod," Edwards says of the simpler design. "The spacing of the frets also doesn't really matter, as the resonances of the strings are not used by this instrument to make the individual notes. You don't need to worry about neck taper, either."

The guitar doesn't have traditional pickups, and it doesn't need tuning — if the strings are tight enough they can vibrate without hitting each other but loose enough they're not flush against the fretboard, it'll play just fine. Instead, the strings and frets themselves act as electrical connections — shorting as you press them down, while reading from the accelerometer as an additional input.

"My prototype of the instrument works and it is super fun to work on and play," Edwards says, "but it is far from perfect. It is finicky to play as you have to manage the weight of the head, holding the instrument up, making gestures, and playing all with the same hand. Furthermore, it is hard to reach every position on the fingerboard since your hand is strapped to the neck."

The project is documented in full on Instructables.