Note the stylish white socks and black shoes combo, too.
I have no idea how he has any sort of lung capacity slouched over like that, let alone how he keeps the trombone slide from hitting the floor.
As an aside, I found this joke when I was checking the correct term for a trombone player:
Q: What do you call a guy who knows how to play the trombone, but doesn't?
A: A gentleman.