It is one of the most recognised sounds in Jewish life. And, whether dedicated shul-goers or three-times-a-year types, we all stand to attention when we hear it. I am talking, of course, of the sound - so familiar at this time of year - of a very special animal horn, the shofar.

Why do we blow it? What is it about this ancient instrument that makes it as symbolic of Judaism as the kippah or the Shabbat candles?

According to tradition, the shofar was blown on Mount Sinai as the Torah was given and, when it is sounded on Rosh Hashanah (also known as Yom Teruah or the "Day of Blasts") and Yom Kippur we are reminded to rededicate ourselves to the Torah and to God.

In the Akedah, the biblical story of the binding of Isaac, when God asked Abraham to sacrifice his son to demonstrate his obedience and faith, the ram and its horns played an essential part. The Talmud says: "Why do we sound the shofar? Because the Holy One said, 'Blow me a ram's horn that I may remember to your credit the binding of Isaac, the son of Abraham'."

It is on this verse from Genesis that the custom of using a ram's horn for the shofar is based but there is no religious law that commands this. It can be made of the horn of an antelope, gazelle or goat - even a Rocky Mountain goat - all of which are kosher, since they have spilt hooves and chew the cud. These horns are not solid bone, but contain cartilage, which can be removed - the word "shofar" means "hollow". Thus, antlers cannot be used; nor can the horn of a cow, as it brings to mind the sin of the golden calf, which is maybe not the best imagery at a time when we traditionally request forgiveness.

Shofar lore
A shofar is measured around the curve, not from tip to tip, and the larger the shofar, the more notes you will be able to play (although the shofar is not an instrument that can be tuned). There are many reasons to pick a given shofar, from its finish (natural or polished) to the size of the mouthpiece (bigger equals easier to play) or the size of the shofar itself.

The shofar itself is not holy - it is only an animal horn - but the sound produced by blowing the shofar on holy days is holy. The Torah does not command Jews to blow the shofar, but to hear it.

An early usage of the shofar was not religious. Today, we think of the shofar's cry as summoning us to shul, to pray, to repent. But, in the ancient world, its sound was a very different kind of rallying call: a declaration of war. Joshua certainly seems to have found it useful at the Battle of Jericho.

In modern Israel, the shofar has still sometimes been used as a rousing battle cry and images exist of Israeli soldiers blowing shofars by the Western Wall or alongside army tanks before heading out to fight.

This tradition of sounding a horn to mark the start of battle has had an impact on the way we use the shofar today. In the rabbinic period, the main Rosh Hashanah service, which includes the blowing of the shofar, took place in the morning. However, it has been said that the enemy (the Romans) heard the Jews blowing their shofar early in the morning, assumed it was a signal for battle - and attacked. So the sounding of the shofar was moved from the morning service to the afternoon.

One memorable, military use of the shofar was when it was used to mark not the start of war, but the end. There are images and video footage from 1945 of Jews blowing shofars after hearing that the Nazis had surrendered.

It has long been the custom to make loud noises on a new year (although nowadays most NYE parties favour speakers over animal horns!). Some believe that, in pagan times, this was to scare away demons for the year ahead. Most Torah scholars believe that blowing the shofar on Rosh Hashanah is not related to this practice, although the Talmud does acknowledge that the shofar has the power to "confuse the accuser". And there is also a rich pagan history surrounding the blowing of an animal horn; for example, to proclaim the coronation of the gods.

Unsurprisingly, all rules and customs, be they Jewish, pagan, celebratory or military, are linked to the sound of the shofar. In the synagogue, the shofar-blower, or Baal Tekiah, recites two blessings then blows a strict sequence of blasts comprised of three different sounds:

Tekiah - starting on a low note, this is uninterrupted and lasts for several seconds and rises; Shevarim - three short-to-medium-length blasts; Teruah - nine short blasts ending with a long, high, final blast (Tekiah Gedola) traditionally three times as long as the Tekiah.

Modern culture has also co-opted the sound of the shofar. In the musical scores to the films Alien and Planet of the Apes, composer Jerry Goldsmith included a role for a shofar in the orchestra. Madonna used one on her 2006 Confessions tour and album. More recently, rap fans may recall rapper Macklemore blowing the shofar in a promotional video for the 2013 MTV Video Music Awards, summoning viewers to watch. (After considerable debate, it was established that the horn he blew was in fact a steer horn - and so not eligible for use in the service.)

It has been a rallying cry to ancient armies, a signal of triumph, a way to bring in the New Year or scare away demons. But, for Jews, whatever its history the sound of the shofar provides an unmistakable, evocative and uplifting experience. 