All three of us trumpet players in my middle school band would sit in the back and have breath holding contests while the director was working with other sections or whatever.

In middle school, I was a swimmer on two teams and played trombone. We had a fun little “who can play the longest note” contest…everyone thought I cheated because I lasted about 30 seconds longer than anyone else. Really wasn’t that hard once you find the right position to use minimal air output, since the game wasn’t who could hold the same note, but any note. We regularly trained on the swim team to go as far as possible underwater in an Olympic pool — record on our team was 4 or 5 round-trips if I recall correctly (can’t remember 100%…long ago…but that kid was crazy in both speed and time underwater).

Pretty demoralizing to be labeled a cheater after such hard work expanding lung capacity and efficiency. After that, I wouldn’t even try anymore just so I wouldn’t be called a cheater again. Quit band the next year.

I wonder if circular breathing would work, or works, for trombone. If so you could have held that note "forever" with some training.

It should given that it works with trumpet (and even voice). I remember listening to some jazz piece on the radio where the DJ, before the song, alerted listeners to the long note that was being held and suggested trying holding your breath for the length of the note (but not—he warned—if you were driving).

It would, which was exactly what I was accused of but wasn’t something I knew how to do…even to this day. I have an idea of the mechanics, I just lack the ability because it has never been something I’ve practiced or developed.