--- title: "Self-playing piano: two Los Angeles engineering students hid 88 solenoids under a secondhand upright’s keys" url: https://badiyaa.com/self-playing-piano-ucla-solenoids-midi/ published: 2026-11-13T10:36:00+00:00 modified: 2026-11-13T10:36:00+00:00 section: Offbeat publisher: Badiyaa --- # Self-playing piano: two Los Angeles engineering students hid 88 solenoids under a secondhand upright’s keys UCLA students Karina Bender and George Grigoryan turned a secondhand upright into a self-playing piano, with 88 MIDI-driven solenoids under the keys. Two UCLA engineering students bought a secondhand upright piano through an online marketplace, hid 88 electric plungers under its keys and taught it to play by itself, right down to slamming every key at once. Karina Bender and George Grigoryan built it in the UCLA Samueli School of Engineering’s Makerspace, and the professor who oversees the space called it the best project in its nearly eight years. Videos of ordinary pianos turned into self-playing ones keep doing the rounds, including a conversion clip that climbed Reddit’s r/nextfuckinglevel this week. The UCLA build, documented by the university, shows how these retrofits actually work. ## A piano key is just a lever The trick starts with simple mechanics. Press a key and its far end tips up a hammer that strikes the strings. A machine does not need to imitate fingers; it only needs to push that lever at the right instant. A standard piano has 88 of them, from a low A to a high C. The UCLA pair did it from underneath. Each key gets a solenoid, an electromagnet that shoves a small rod upward when current flows. A laptop reads a MIDI file, the digital music format from the 1980s, and software sends one pulse per note to a set of microcontrollers, which fire the matching solenoids. Getting the hardware right was the hard part. Small solenoids were too weak, and strong ones would not fit side by side under the keyboard. The students staggered them in three rows on a custom board, using longer rods for the rows farther back. Then the rods missed their keys, so they added 3D-printed aligners and an anti-rotation holder. The first playback, Bender said, sounded bad. On November 3, 2025, it finally played a recognizable song: Chopin’s “Revolutionary” Étude in C minor. ## Why all 88 keys at once is hard A human pianist rarely needs more than 10 keys down at once. The students wanted all 88 for the meme piece “Rush E,” which ends with chords no person could play. According to the university, powering every solenoid together draws five to 10 times the current of a kitchen toaster. Here is the rough math. A typical toaster draws about 7 to 10 amps on a US circuit, so the full-keyboard slam lands somewhere between about 35 and 100 amps. Hobby builds avoid that. One maker who goes by GotGaMeR, whose solenoids each pull about 1.6 to 1.7 amps, told an interviewer he sized his power supply for roughly 20 keys at a time. At that draw, 88 keys would need close to 150 amps. ## From paper rolls to MIDI The idea is more than a century old. The [player piano](https://en.wikipedia.org/wiki/Player_piano) took off after Edwin S. Votey invented the Pianola in 1896, a foot-pumped machine that used air flowing through holes in a paper roll to strike notes. An industry meeting in Buffalo, New York, in 1908 standardized an 88-note roll so any player could read any make. Sales peaked in 1924, before radio and better phonographs took over. - 1896: the pneumatic Pianola - 1904: Welte’s reproducing piano captures a pianist’s phrasing - 1982: Yamaha’s digital Piano Player, replaced by the Disklavier in 1987 - Today: MIDI-driven solenoids, sold as retrofit kits or built by hobbyists Commercial conversion kits usually mean cutting open the bottom of the piano to fit parts under the keyboard. Some makers, like GotGaMeR, instead sit a rail of solenoids on top of the keys so it works on almost any instrument. The sound is still acoustic: hammers hit real strings, unlike a digital piano. For more musical oddities, see our story on [Liszt’s La Campanella on a toy piano](https://badiyaa.com/la-campanella-liszt-toy-piano/) and the [Offbeat section](https://badiyaa.com/category/offbeat/). The UCLA team wrote a 30-page build manual, and its next goal is volume control, since the piano currently plays at a single loudness, with no pianissimo. ## Further reading - [Wikipedia: Player piano](https://en.wikipedia.org/wiki/Player_piano) - [UCLA Samueli: self-playing piano](https://www.samueli.ucla.edu/how-two-ucla-engineering-students-built-a-self-playing-piano-that-can-do-the-impossible/) *Image: nwclassicyacht, CC BY 2.0 via Wikimedia Commons* *This article was produced with AI assistance and reviewed by our Editorial Desk. [How we work](https://badiyaa.com/editorial-policy/).*