The euphonium is a medium-sized, 3-valve, conical-bore, tenor-voiced brass instrument. Sound is produced when the player's vibrating lips (embouchure) cause the air inside the instrument to vibrate. Like the trumpet, putting down different combinations of valves changes the length of the tubing, and produces different notes. The euphonium is similar to the tuba, but of a smaller size and therefore higher pitched. The euphonium can have a bright, moderate, or dark tone depending on the register.