Put it on a laptop or TV, everyone scans the QR, and each phone gets a few strings of the same guitar. Tap your dot when it hits the ring and the big screen plays your note; miss and the song has a hole in it. Nobody holds a guitar, but the room plays one.

In the clip four phones play House of the Rising Sun, and at 0:12 the bass phone leaves. The song keeps going with a gap where the low notes were. It's four phone screens recorded in a browser, not a filmed room.

The part I fought with longest was dealing the strings: a string that would sit silent for two bars merges into its neighbour, so nobody stands there waiting. One phone alone gets every string and it's a plain rhythm game.

Free, no account, nothing to install: https://overflow.games/unison/?door=lemmy-gamedev

If you've built local multiplayer: what broke first for you, the latency or the people?