From the Groves Music Online article on Alphorn:
"Alphorn [Alpenhorn] (Ger.; Fr. cor des alpes).
Wooden trumpet of pastoral communities in the Alps. The name is also conveniently used to cover similar instruments of Scandinavia, Russia, the western Slav countries, Hungary, Romania and, up to the 19th century, some of the highlands of Germany. Szadrowsky's vague reports of alphorns in the Pyrenees and the Scottish highlands are unconfirmed. An alphorn is made of a young fir, lime, poplar etc.; a mountainside tree curving upwards from the roots is often chosen, giving an upturned bell. The wood is longitudinally halved by axe or saw and each half is hollowed. The two pieces are reunited under strips of bark or binding of roots or gut. The mouthpiece may be either cut in the wood or made separately. In several areas the folded shape of a trumpet is sometimes imitated. The commonest length of the alphorn is about 185 cm, in which case its range extends to the 5th or 6th harmonic (as quoted by Beethoven at the end of the Pastoral Symphony). Many alphorns are 120 cm in length or less; however, instruments 335 cm long have been known in Switzerland since the 16th century, and specimens up to 520 cm occur in Slovakia. Today the standard length ranges from 340 cm to 360 cm for alphorns tuned in F or G. Tunes may then ascend to the 12th harmonic or even higher.
Alphorns were known best as herdsmen's calling instruments, serving also in some areas to summon to church and formerly to war. They may also be numinous: among the Mari of Russia the long wooden trumpet is made for the spring festival and afterwards sacrificially burnt or hidden in a sacred place. Overall likeness in making and using alphorns, and their distribution, suggest that they possibly may have originated among post-Celtic peoples of the Migration Era. There is no firm evidence of prior existence; ‘cornu alpinus’ in Tacitus is less than proof of a wooden trumpet, of which the earliest specimen, from the 9th-century Oseberg ship (Oslo, Vikingskiphuset), supports iconographic suggestions that wooden trumpets of moderate size were used as summoning and military instruments in early medieval northern Europe in addition to their pastoral functions."
Some Alphorn Ensemble Links:Boston Globe Article
Rocky Mountan Alphorns
St. Moritz Alphorn Ensemble
International Alphorn Society
New Jersey Workshop for the Art
Swiss Alpine Music