When was the shoulder rest for violins invented, and when did it come into widespread use?
According to this article, the shoulder rest was a mid 20th Century invention. However, the author also seems to imply that the 'unofficial version' of the shoulder rest was in use even in the time of the invention of the chin rest - the "shoulder pad."
Should we decide rather to take Prinner's and Leopold Mozart's advice and use the chin-on position, there is one very important consideration, which is quite simply not mentioned in any of the 17th or 18th century sources; - namely, how to get the chin close enough to the violin to support it, without the use of some kind of shoulder pad (first mentioned by Baillot in 1834), a chin-rest (invented around 1820 by Spohr), or even more extreme, a shoulder rest (a mid 20th century invention).
This professor seems to think it was invented in the 1920's-30's, more specifically.
Ultimately, the fact that there seems to be no specific date to 'pin-down' the invention of a thing that has become such a staple of use and debate in the music world seems to give credence to the idea that the old shoulder pad had already been in use to achieve the same effect long before the 'shoulder rest' was an actual thing.
I didn't write this, I'm just copy pasting. Taken from here:
Here's the post:
The first actual (American) patent I can find for something that is actually a specific shoulder rest (actually a shoulder rest/chin rest combo) and not a pad, is dated 2/9/1909, issued to G. Becker as patent number 908541. You can find it at the US Patent search site. In the text it is referred to as an improvement to such rests already available! From that we can deduce that such rests, at least like this one, were already available on the market, if not in common use (but one assumes that they would not be on the market if they didn't sell, and therefore must have been used by some players). Unfortunately, Becker does not reference the patent or patents or device that he is improving on, and considering the date, it's possible that some similar devices actually had no patents (though not likely).
An interesting side note is that, if one studies patents, it will be seen that often the actual device eventually sold does not always resemble the drawings patented, although they must include the basic features to protect the patent..
This assumes a lot I admit, but to me it indicates that specific shoulder rests were in use at least on or before that date.
Another interesting patent issued to a Colbertson on 4/29/1930 as patent number 1756676, seems to be designed to give a padded edge to the bottom plate for players that did not normally use a rest, but didn't like the feel of the plate edge on the collarbone. It is similar to something I tried to come up with a few years ago but failed. There are many other patents listed as one approaches the present.
Again, I am assuming a lot here, but this info seems to indicate that specific use shoulder rests (not pads) were in use at least by the turn of the last century, and are not a recent development, although considering the lifespan of the violin, I suppose it could be considered recent.