Few aspects of string playing are more divisive, or inspire such strong reactions, as the topic of the shoulder rest. Some players swear by them; others swear at them.
While no one can have a definitive word on such an personal topic, let's have a look at some of the issues surrounding shoulder rests, and see if we might bring some clarity to the subject.
We should approach any discussion of shoulder rests with a basic idea in mind: that we are striving to integrate the balance of the instrument into the balance of the body. This integration allows the player's body to function unimpeded by unnecessary muscular tension needed to hold an out-of-balance body in place.
Now, a shoulder rest should serve this integration by providing height and stability to the instrument. Let's look into how a shoulder rest might help the playing experience by by offering those, in the following discussions.A good first question is: how much height should a shoulder rest bring to a player?
Players often have attempted to fill the distance between the shoulder and the jaw by using tall shoulder rests and low chinrests.
However, this brings the instrument up into an often awkward height relative to the shoulders, forcing the player to "climb" the instrument with their bow arm in order to play on the lower strings, play toward the frog, etc.
In addition, moving the bow arm up to reach that higher point can result in extra muscular effort needed to maintain that hold, resulting in a stiffness that can harm spiccato and other small bow motions.
For the left hand, the higher position for that hand can effect tension in the left shoulder, and it also can negatively affect the angle at which the fingers address the strings.
Let's think about a lower shoulder rest.
If we use a taller chinrest and a lower shoulder rest, the instrument is brought down to a level closer to the shoulders. Less effort is needed to raise the arms to reach the instrument, and the weight of the right arm is applied more directly to the strings, resulting in a fuller, deeper, richer sound.
How to support the instrument from below, and what are some ideas for shoulder rests?