 The more common "double horn" has a fourth, trigger valve, usually operated by the thumb, which routes the air to one set of tubing tuned to F or another tuned to B which expands the horn range to over four octaves and blends with flutes or clarinets in a woodwind ensemble.Triple horns with five valves are also made, usually tuned in F, B, and a descant E or F. There are also double horns with five valves tuned in B, descant E or F, and a stopping valve, which greatly simplifies the complicated and difficult hand-stopping technique, though these are rarer.Also common are "descant" doubles, which typically provide B and alto F branches.