The euphonium is a medium-sized, 3 or 4-valve, often compensating, conical-bore, tenor-voiced brass instrument that derives its name from the Ancient Greek word εὔφωνος euphōnos, meaning "well-sounding" or "sweet-voiced". The euphonium is a valved instrument. Nearly all current models have piston valves, though some models with rotary valves do exist.
Euphonium
A euphonium (left) and tuba (right), the two lowest conical-bore instruments
Double bell euphonium by Conn
King marching euphonium
A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called labrosones or labrophones, from Latin and Greek elements meaning 'lip' and 'sound'.
Six high brass instruments Left, from top: A reproduction baroque trumpet in D, a modern trumpet in B♭, a modern trumpet in D, a piccolo trumpet in B♭ (octave higher), and a flugelhorn in B♭. Right: a cornet in B♭.
A tenor horn (alto horn) in E♭, baritone horn in B♭, and euphonium in B♭
Brass instrument piston valves
Flugelhorn with three pistons and a trigger