Q: I know that Fender amps tended to call the tremolo effect “vibrato” and their vibrato tailpiece “tremolo.” My question is this: Did Fender actually ever have a vibrato effect on its amps? Did any manufacturer?
A: That’s an interesting question! No, Fender never had a true vibrato effect, but more than a few players who were around in the 1950s believe that Fender used the term in order to compete with the Magnatone line, which, beginning in the late 1950s, actually released a series of amplifiers with true vibrato – that is, with pitch modulation rather than amplitude modulation. That was the 200 Series, which appeared in about 1957 in the Model 260 and 280. By the early 1960s, the Magnatone 50-watt 280-A began to incorporate a “mellow” switch, for use by accordionists who had pickups installed on their instruments, along with a “bright” switch for guitarists. It also included the true stereo vibrato circuit, two 12″ speakers, and two 5″x7″ or 6″ tweeters, which were also ahead of their time.
As an aside, the first true tremolo circuits appeared in Gibson, Danelectro, and Premier amplifiers as early as the 1940s. It wasn’t until 1955 that Fender introduced tremolo into their amplifier line (and called it by its correct name) with the release of the Tremolux amp. This somewhat reinforces the possibility that Fender changed the term to vibrato post-1959. However, all of that is pure conjecture, and Fender has been manufacturing high-quality amplifiers for so long that it would be impossible (and unfair) to put together a clear picture of why certain features were given certain names.