I 3D-printed a working trombone!
It's mostly based on the design from https://www.youtube.com/watch?v=OI0A-zdRvIk but the 3D printer I used is too small to print some of those parts, so I had to get a bit creative with cutting and gluing/taping.
In theory it should sound decent, but I'm pretty bad at playing the trombone. See the end of that video for a demo by someone who actually knows how to play the instrument.



