Three valves control the flow of air in the single horn, which is tuned to F or less commonly B♭. The more common double horn has a fourth valve, usually operated by the thumb, which routes the air to one set of tubing tuned to F or another tuned to B♭. Triple horns with five valves are also made, tuned in F, B♭, and a descant E♭ or F. Also common are descant doubles, which typically provide B♭ and Alto F branches. This configuration provides a high-range horn while avoiding the additional complexity and weight of a triple