During the crusades – the nine wars fought between western Christians and eastern Muslims over who controlled the Holy Land, 1095–1291 – the Christian armies faced massed bands of Saracens playing piercingly loud double reed instruments called zurnas, used as a psychological weapon. The zurna is the Arabic predecessor of the European shawm. If you have ever stood near even a single shawm player and felt your bones shake, you can imagine the effect.
(The U.S. Army use loud music as a war weapon today. Remember how President of Panama, Manuel Norriega, was ousted with constant loud rock music played by the U.S. Army in 1989? And the use of constant loud music by the U.S. Army to wear down David Koresh and Branch Davidian in the Waco siege of 1993?)
Mediaeval Europeans must have liked the exciting and raucous zurna, as they began to make their own. They mellowed the tone by almost doubling its length, modified the mouthpiece for greater note control, and used it for listening, dancing and military purposes: thus the shawm was born. It became a very popular European instrument from the 13th to the 17th centuries, especially outdoors, for obvious reasons. Shawms accompanied by sackbuts (the predecessor of the trombone) were typically used by the waits bands which flourished in Europe from the 15th to the 19th centuries, standing watch on the city wall at night and playing music for official occasions.
From the beginning of the 16th century, shawms were made in several sizes, from the high sopranino to the super-low great bass. Four and five part music could now be written for a shawm consort, to be played at royal and court events. It really is a fabulous and exciting sound, best heard from the opposite end of a very large field.
Shawm playing a ductia, anon., France, c.1300