The Shofar is the ritual instrument of the ancient and modern Hebrews, the only Hebrew cultural instrument to have survived until now. Of martial origin, the shofar was a priestly instrument in Biblical times. According to the Mishna, two different forms of shofar were used in the Temple: one made of ibex horn, its bell ornamented with gold, was sounded at New Year and during the Yovel Days; one made of ram's horn with silver ornamentation was sounded on fast days. We learn from the Mishna and the Talmud that in the Hellenistic period no improvements or modifications that might affect the tone were permitted: no gold-plating of its interior, no plugging of holes, no alteration of its length (the minimum permissible length of a ritually approved horn was 3 handbreadths); the shofar tone was to be preserved unaltered. Nor was the process of steaming or boiling permitted. Apart from its liturgical uses the shofar was closely connected with symbolism. Its blast destroyed the walls of Jericho, and in the Dead Sea scrolls we read that during battles shofar blowers sounded a powerful war cry to instill fear into the hearts of the enemy while priests blew the six trumpets of killing. Historically the shofar has also served in a number of popular usages: it was sounded during rites to bring rain, in the event of local disasters, and so on. In our times its liturgical use is restricted to New Year (Rosh Hashanah) and the Day of Atonement (Yom Kippur). Israel used the shofar or the silver trumpets to call allembly, to signal sacrifice or to panic the enemy in battle. However, Numbers 10:7 says (But when the congregation is to be gathered together, ye shall blow, but ye shall not sound an alarm.) The Jews honored this command. These sounds seem to connect us to the ancient Hebrews being called to prayer or worshipful silence before God. The shofar is a ram's horn which is blown somewhat like a trumpet. One of the most important observances of this holiday is hearing the sounding of the shofar in the synagogue. A total of 100 notes are sounded each day. There are four different types of shofar notes: tekiah, a 3 second sustained note; shevarim, three 1-second notes rising in tone, teruah, a series of short, staccato notes extending over a period of about 3 seconds; and tekiah hagedolah (literally, "The last Trumpet"), the final blast in a set, which lasts (I think) 10 seconds minimum.  The Bible gives no specific reason for this practice. One that has been suggested is that the shofar's sound is a call to repentance.