Earlier this month I went to see Michael Kac, a professor in my department and an accomplished banjo player, talk about authenticity and adaptation in the performance of folk music. At some point he mentioned in passing that violin vibrato is an artifact of the development of audio recording technology. Interesting!
I tracked down a book chapter titled "Aesthetics out of Exigency: Violin Vibrato and the Phonograph" (In Capturing Sound by Mark Katz) that discusses the issue in detail. It looks like the case isn't quite as cut-and-dried as Dr. Kac made it out to be, but there's pretty good reason to think that violin vibrato is, indeed, a phonograph effect.
The recorded evidence clearly suggests an abrupt change in style. In the earliest days of recording-- prior to 1910-- vibrato is rarely used. By 1920, continuous vibrato like we are used to today was the norm. This decade corresponds with an explosion in the number of recordings, and in the adoption of phonographs in the home.
Why think there's a causal link in this correlation?
Katz dismisses a few competing explanations. Continuous vibrato probably isn't a simple matter of changing taste, because the continuous vibrato was panned by critics at the time. Continuous vibrato can't be the effect of the introduction of the chin rest (which frees up the left hand), because the chin rest was adopted nearly a century before. Nor can it be the effect of the transition to metal strings. Gut strings weren't widely abandoned until the 1920s, and continuous vibrato on gut strings is common in recordings from the late teens and early 20s.
Katz' suggestion: it was the awkward nature of early recording studios that urged the switch to continuous vibrato. In the early days, microphones hadn't yet been invented, and recording was an entirely acoustical affair. You'd sing or play into a huge horn, like the sound horns on old Victrolas. The sound waves, focused by the horn, made a needle vibrate, and the needle scratched a groove in a wax cylinder.
This purely acoustic setup wasn't very sensitive to low-volume noise, and the violin is a low-volume instrument. So, in order for soloists to be heard on a record, they had to lean partway into the recording horn. Since, in addition to being low-volume, violins are especially active instruments, this was a high-risk solution. If a soloist bumped the recording horn with the bow, the take would be ruined.
Violinists soon discovered that the throbbing pitch changes of vibrato projected sound into the acoustic horns better than a steady pitch. This allowed them to record without sticking their heads inside the horn, and so the technique spread rapidly in recording studios. As records-- as opposed to concerts-- became the main way listeners accessed classical music, they came to expect vibrato in concerts, too. And before long, classical music was dominated by continuous vibrato on the violin. None of us alive today have heard it any other way.
Anyway. This idea of the phonograph effects-- ways in which recording technology has changed music, instead of merely documenting it-- is neat. The vibrato chapter was easily the best one in the book, but the book as a whole was good enough to have me on the lookout for phonograph effects everywhere I look. I think maybe there's one somewhere in Brian Eno...