What they don't tell you about starting a band is that the hardest part is organizing the people. So, why not skip that step and build a bunch of MIDI controlled robots to play music with?

In this project, you'll mount servo motors over the strings of a lyre. The servos will pluck those strings when they receive MIDI NoteOn messages via a Feather RP2040 running CircuitPython. You can control the lyre with an eternal MIDI controller or by sending MIDI out from your favorite DAW program.

The entire build sits on a plate of acrylic with some 3D printed parts. The servos have 3D printed horn extenders to pleasantly pluck the strings.

The servos are driven by the PCA9685 servo driver breakout. The driver board has an external 5V power input and connects to the Feather RP2040 over I2C.

A Note on Robotic Instruments

All acoustic instruments are slightly different and, as a result, if you build this project, you may need to do some fine tuning to the mechanical aspects of the design for best results. This lyre was used for the build because it seems to be a common shape for budget lyres and is from a known budget music brand (Donner).

The parts that were the most finicky to dial in were the servo horns and the acrylic pegs that lift the acrylic base. It's important to achieve a proper balance between these two measurements for the best timbre from the lyre, with less than a millimeter often making a difference. All of the design files are included and should work as-is, but the source files are also available if you find you need to adjust things.


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This guide was first published on Mar 22, 2023. It was last updated on Jun 20, 2024.

This page (Overview) was last updated on Mar 08, 2024.

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