A trumpet is a brass instrument in the key of Bb in the higher register but a Euphonium is in the lower register. It is a versatile instrument and can be used in various musical genres like orchestras, concert bands, and jazz ensembles. The euphonium's warm, lyrical sound can be described as somewhere between a tuba and a trombone. Just like other brass instruments, players change pitches on a euphonium by pressing different combinations of keys and moving a slide.