Do you puff your cheeks when play the trombone?

Yes, trombonists puff their cheeks when they play. This is done to create a larger oral cavity, which helps to produce a fuller, richer sound. When a trombonist puffs their cheeks, they are essentially creating a resonance chamber that amplifies the sound of the instrument. This technique is also used by other brass players, such as trumpet and tuba players.