 You can build a musical instrument with Adafruit's ARP2040 Propmaker Feather and Circuit Python. The Synth guitar is a 3D-printed polyphonic synthesizer featuring Neoki switches and Stemma QT rotary encoders. We think it's a fun and interesting toy instrument that showcases Circuit Python's Synth I.O. Powered by the ARP2040 Propmaker Feather, this dev board has everything you need for building a synthesizer with high quality digital audio. The design is inspired by the iconic SG guitar in a smaller body that's about 20 inches long. Toggle switches let you play different modes and the rotary encoders adjust modulation, note octaves, and volume. Inside the headstock is a 3W speaker and the neck features 8 backlit Neopixel key switches. There's also Neopixels that change colors depending on the note being played. Circuit Python's Synth I.O. module lets you create small yet powerful polyphonic synthesizers with minimal hardware. In the code you can change the parameters of the envelope or the notes that you want to play. You can also tweak the frequency of the filter and the waveform to sculpt your own sound. There's a whole breakdown of how the code works in the Project Learn Guide along with Step-by-Step Assembly and the source files. We think this project is a good starting point for folks who want to build their own synthesizers. Inspired by Guitar Hero's Game Controller, you can strum like a guitar player and play notes and chords. You can turn off strum mode and play notes using just the Neo keys. This becomes handy when playing solos. The accelerometer controls high and low pass filters. Tilt the guitar up for high pass and down for a low pass. The middle encoder lets you adjust the LFO rate of the tremolo effect. You can press the encoder to turn it on and off. Turn the next rotary encoder to adjust the octave range or the pitch of the notes. Pressing this encoder switches between triad and diatonic notes. If you mix all of these together, we think you can get really creative with your playing styles. We designed the synth guitar to be 3D printed but you could modify the parts for other forms of manufacturing and in different materials. You can download our design source file to change the overall design or use our 3D models of the electronics to create your own custom instrument. We had a lot of fun working on this project and hope it inspires you to check out the RP2040 prop maker in the synthio module in circuit python.