The shofar is sounded on the high holy days, and the tradition is careful to distinguish it from music: it is a wordless cry that the law requires, not a performance.
Prescribed calls
The shofar produces a small set of prescribed calls, a long blast, three broken notes, nine staccato ones, and the sequence is fixed, counted and legally required rather than freely performed. A ram horn is preferred for the association with the ram caught in the thicket in Genesis 22, and cow horn is excluded, traditionally because of the golden calf. The rabbinic literature is comfortable saying that the sound means more than it says, and it is described as a wordless cry rather than a melody.
A test of Jewish safety
The shofar has also been a marker of what Jewish practice a place will tolerate. It was blown at the Western Wall at the close of Yom Kippur throughout the British Mandate in defiance of a ban imposed in 1930 after the 1929 riots, and men were repeatedly arrested for it until the ban ended with the Mandate. Like the hanukkiah placed in a street-facing window, the shofar is an audible practice whose freedom or suppression has served as a barometer of Jewish security.