You are not supposed to put things inside a piano. The Brazilian pianist Vinheteiro tips hundreds of glass marbles across the strings of a grand and plays it anyway, and the instrument comes back changed rather than broken.

The picture does most of the work here: a concert grand with its lid up and its entire string bed under a layer of coloured glass, marbles caught mid-bounce over the bass strings as the hammers land underneath. It is a genuinely beautiful image of a thing nobody should do.

What it sounds like is the interesting part. The marbles sit on the strings and damp them unevenly, so each note comes out with a rattle riding on top — the fundamental still there, roughened, buzzing where it used to be smooth. And because the strings move, the marbles never settle: they hop and reseat with every strike, so the same note played twice does not quite match. The piano stops behaving like a fixed instrument and starts behaving like a surface.

There is a real tradition behind the stunt, whether or not the video reaches for it. John Cage spent the 1940s wedging bolts, screws and rubber between piano strings and calling the result a prepared piano — the Sonatas and Interludes are the canonical outcome. What is on screen is the same principle assembled from the cheapest possible material, and arriving at a percussive, faintly gamelan-like result by accident rather than by score.

Vinheteiro — Fabrício André Bernard Di Paolo, on the channel @Lord_Vinheteiro — has form for this: an earlier video plays a piano using typewriters. Nothing here needs a musical education to enjoy, which is most of the appeal. You watch a man in black tie ruin a piano’s tone on purpose, and the piano turns out to have more in it than expected.