The hardest part of any stringed instrument robot has to be getting many moving parts to agree on timing, and that is where this build shines. The maker has spent six years iterating on the mechanical design, the electronics, the software, and the calibration and testing, and it shows. Instead of programming every motion by hand, the software takes MusicXML files exported from notation software and turns them into the fretting, picking, and timing commands the ESP32 sends out.
The construction is a nice mix of printed and off-the-shelf parts. White 3D-printed frames, gears, and linkages sit along a Yamaha acoustic guitar, with servo motors mounted on the neck for fretting and over the body for picking. Numbered actuators, labeled with values like 31 through 36, press the strings down onto the frets, and each one lifts off under software control rather than using solenoids. The actuators are wired back to a central control circuit board mounted beside the neck.
My favorite detail is the orange pick mechanism at the sound hole. It plucks individual strings and moves vertically using rack-and-pinion gears driven by servos, which seems like a clever way to reach any string without redesigning the whole picker. Fretting with servos instead of solenoids also looks like a deliberate trade in favor of control over speed.
The performance of the Sweet Dreams melody for Halloween is the payoff, and the maker is upfront that timing, reliability, and overall performance are still being refined. String noise on release is the current sticking point, since lift speed and timing change how it sounds, and there is no dedicated muting mechanism yet.