Wikipedia
Steerhorn
The steerhorn ( German: stierhorn, also known in English as a cowhorn or bullhorn) is an extremely long medieval bugle horn. The instrument has been used both orchestrally and in war.
The steerhorn has a straight tube with an exact conical bore and no bell flare.
The steerhorn is used in Wagner's Der Ring des Nibelungen, as the score requires one steerhorn in Die Walküre and four in Götterdämmerung. Today, many orchestras substitute the trombone or bass trombone. The Solti recording, the Golden Ring, had a steerhorn specially made as American soldiers carried off Bayreuth's steerhorns after the end of World War II.