The alphorn or alpenhorn or alpine horn is a labrophone, consisting of a natural wooden horn of conical bore, having a wooden cup-shaped mouthpiece, used by mountain dwellers in Switzerland and elsewhere. Similar wooden horns were used for communication in most mountainous regions of Europe, from French Switzerland to the Carpathians.

For a long time, scholars believed that the alphorn had been derived from the Roman-Etruscan lituus, because of their resemblance in shape, and because of the word liti, meaning Alphorn in the dialect of Obwalden. There is no documented evidence for this theory, however, and, the word liti was probably borrowed from 16th-18th century writings in Latin, where the word lituus could describe various wind instruments, such as the horn, the crumhorn, or the cornett. Swiss naturalist Conrad Gesner used the words lituum alpinum for the first known detailed description of the alphorn in his De raris et admirandis herbis in 1555. The oldest known document using the German word Alphorn is a page from a 1527 account book from the former Cistercian abbey St. Urban near Pfaffnau mentioning the payment of two Batzen for an itinerant alphorn player from the Valais.

17th-19th century collections of alpine myths and legends suggest that alphorn-like instruments had frequently been used as signal instruments in village communities since medieval times or earlier, sometimes substituting for the lack of church bells. Surviving artefacts, dating back to as far as ca. AD 1400, include wooden labrophones in their stretched form, like the alphorn, or coiled versions, such as the '"Büchel" and the "Allgäuisches Waldhorn" or "Ackerhorn". The alphorn's exact origins remain indeterminate, and the ubiquity of horn-like signal instruments in valleys throughout Europe may indicate a long history of cross influences regarding their construction and usage. This instrument is also used on the Ricola commercials.

The alphorn is carved from solid softwood, generally spruce but sometimes pine. In former times the alphorn maker would find a tree bent at the base in the shape of an alphorn, but modern makers piece the wood together at the base. A cup-shaped mouthpiece carved out of a block of hard wood is added and the instrument is complete.

The alphorn 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 alphorn made at Rigi-Kulm, Schwyz, and now in the Victoria and Albert Museum, measures 8 ft. in length and has a straight tube. The Swiss alphorn varies in shape according to the locality, being curved near the bell in the Bernese Oberland. Michael Praetorius mentions an alphorn-like instrument under the name of Hölzern Trummet (wooden trumpet) in Syntagma Musicum (Wittenberg, 1615-1619; Pl. VIII).

The notes of the natural harmonic series overlap, but do not exactly correspond, to notes found in the familiar chromatic scale in standard Western equal temperament. Most prominently within the alphorn's range,the 7th and 11th harmonics are particularly noticeable, because they fall between adjacent notes in the chromatic scale.(audio)

In the hands of a skilled composer or arranger, the natural harmonics can be used to haunting melancholy effect or, by contrast, to create a charming pastoral flavor, as in the lilting Ranz des Vaches and works by Brahms, Rossini, and Britten cited below. Similar to the view of Leopold Kronecker that "God made the integers; all else is the work of man," musicians drawn to the alphorn and other instruments that sound the natural harmonics, such as the natural horn, consider the notes of the natural harmonic series] — particularly the 7th and 11th harmonics — to be God's Notes, the remainder of the chromatic scale enabled by keys, valves, slides and other methods of changing the qualities of the simple open pipe being an artifact of mere mortals.

The well-known Ranz des Vaches (score ; audio) is a traditional Swiss melody often heard on the alphorn. The song describes the time of bringing the cows to the high country at cheese making time. Rossini introduced the Ranz des Vaches into his masterpiece William Tell, along with many other delightful melodies scattered throughout the opera in vocal and instrumental parts that are well-suited to the alphorn. Brahms was clear that the inspiration for the great melody that opens the last movement of his First Symphony (played in the orchestra by the horn) was an alphorn melody he heard in the Rigi area of Switzerland. Finally, the prologue to Britten's Serenade for Tenor, Horn and Strings, played on horn without the use of valves but equally suited to the alphorn, is a beautiful, inspired example of the lyric possibilities of natural harmonics.

Among music composed for the alphorn:

• Sinfonia Pastorella for Alphorn and String Orchestra by Leopold Mozart
• Concerto for alphorn and orchestra by Jean Daetwyler
• Concertino rustico by Ferenc Farkas
• Begegnung, for 3 alphorns and concert band, by Kurt Gable.
• Säumerweg-Blues (audio played by Kurt Ott) among many compositions by Hans-Jürg Sommer, Alphorn Musik
• Messe für Alphorn und Chor by Franz Schüssele Alphorn-Center

• Eliana Burki, jazz and modern alphorn; Chillout (audio)
• William Hopson, traditional and modern alphorn; also horn player (Calgary Philharmonic) and alphorn builder
• Joszef Molnar and his Swiss Alphorn Quartet
• Kurt Ott, jazz and modern alphorn
• Arkady Shilkloper, jazz and modern alphorn

• "Alpentraum" Michigan, USA
• Alphorn Academy of Switzerland
• "Chrystal" (in German)
• Frances Jones UK alphornist
• Jacaranda Ensemble (World music, featuring alphorn)
• "Les Briançonneurs" Briançon, France
• Mike Cumberland
• Swiss Alphorn Players (in German)

• William Hopson, Rocky Mountain Alphorns
• Alain Prouvé, Briançon, France
• Roger Zenetti (maker of the "Alpflyinghorn," a tuneable, collapsable carbon-fiber alphorn)
• Alphornbau Josef Stocker
• Pete Wutherich, of Boise, Idaho, who with Josef Stocker competed to build the world's longest alphorn. While both eminent masters preliminarily tied in a photo finish at 154 feet, 8 inches long (the nose alone fitting into the frame), according to Wutherich, his stealthy work on the bell of his magnum opus resolved the friendly competition in his favor. At 89, Wutherich decided that the time had come to part with his champion.

• Bachmann-Geiser, Brigitte, Das Alphorn: Vom Lock- zum Rockinstrument. Paul Haupt, Berne, 1999. ISBN 3-258-05640-4
• Franz Schüssele, Alphorn und Hirtenhorn in Europa, book and CD with 63 sound samples available at Alphorn-Center,ISBN 3-927781-21-5

• Alphorn in concert Concert and composition contest taking place annually in Oensingen, Canton Solothurn, Switzerland
• Hans-Jürg Sommer, links
• International Alphorn Festival in Nendaz, Canton Valais, Switzerland
•  Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)