Shoulder rest
From Wikipedia, the free encyclopedia
The shoulder rest is an accessory that can be found on violins and violas. It may be made of wood, aluminium, carbon fiber or plastic. Usually, the shoulder rest attaches to the edge of the back of the violin with "feet" padded with rubber tubing or made of soft plastic.
Without a shoulder rest, a violinist may raise their shoulder, to bring the violin closer to the jaw and hold the instrument in place, particularly when shifting positions. Problems usually surface doing this, such as muscle tension which obstructs fluidity of technique, and may lead to injury in the long term. The shoulder rest's function is to allow a natural, comfortable attitude while playing. It can also hinder the instrument's tone because it decreases the sound vibrations dramatically. Many professional violinists prefer to not use a shoulder rest. Depending on body type, some musicians may need no more than a sponge or cloth under the instrument instead of a shoulder rest.

