A brass instrument that is typically used in place of the horn in marching bands or drum and bugle corps.

The mellophone has 3 valves and the keys are pressed with the right hand. The fingerings of the mellophone are identical to the fingerings of a trumpet, though alternate fingerings on higher notes often are more in tune than normal trumpet fingerings. Mellophones are typically pitched in the key of F. The overtone series is an octave above that of the horn.

The main reason that the mellophone is used in place of the horn for marching is that the mellophone is a bell-front instrument, so that the sound goes in the direction that the player is facing. Although, the marching French horn also has this same bell-front configuration, mellophones are usually constructed with a larger bore for louder volume than marching French horns.