We don't have synonyms for alpenhorns yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are alpenhorn and alphorns.
(n) :
Alternative spelling of alphorn. [(music) A long, curved, wooden horn used by mountain-dwelling herders in the Alps, originally to call cattle but now only as musical instrument in classical and folk tunes.]
(n) :
Alternative spelling of alphorn. [(music) A long, curved, wooden horn used by mountain-dwelling herders in the Alps, originally to call cattle but now only as musical instrument in classical and folk tunes.]