Alpenhorn or alphorn, a wind instrument, consisting ofa natural wooden horn of conical bore, having a cup-shaped mouthpiece, used by mountaineers in Switzerland and elsewhere.

The tube is made of thin strips of birchwood soaked in water until they have become quite pliable; they are then wound into a tube of conical form from 4 to 8 ft. long, and neatly covered with bark. A cup-shaped mouthpiece carved out of a block of hard wood is added and the instrument is complete.

The alpenhorn has no lateral openings and therefore gives the pure natural harmonic series of the open pipe. The harmonics are the more readily obtained by reason of the small diameter of the bore in relation to the length. An alpenhorn made at Rigi-Kulm, Schwytz, and now in the Victoria and Albert Museum, measures 8 ft. in length and has a straight tube.

The well-known Ranz des Paches is the traditional melody of the alpenhorn, which has been immortalized by Beethoven in the finale of the Pastoral Symphony, where the music is generally rendered by a cor anglais. Rossini has introduced the melody into his opera William Tell. Wagner, in the third act of Tristan and Isolde, was not entirely satisfied with the tone quality of the cor anglais for representing the natural pipe of the peasant. Having in his mind the timbre of the alpenhorn, he had a wooden horn made for him with one valve only and a small pear-shaped bell, which is used at Bayreuth.

The Swiss alpenhorn varies in shape according to the locality, being curved near the bell in the Bernese Oberland. Michael Praetorius mentions the alpenhorn under the name of holzerni trummet in Syntagma Musicum (Wittenberg, 1615-1619).