Vibrato unit

A few guitar amplifiers do feature true pitch shifting vibrato, notably some models offered in the late 1950s and into the 60s by Magnatone[2][3] and presently by Juke Amplification[citation needed].

Still other amplifier manufacturers describe the effect, in accordance with standard music terminology, as tremolo.

Danelectro, Gibson, and Premier all produced guitar amplifiers with built-in amplitude modulation units in the late 1940s.

A vibrato unit normally has three controls: The term "vibrato unit" was introduced on high-end Fender guitar amplifiers in the 1950s, starting with the Vibrolux amplifier in 1956, in the same period in which what is now called a "tremolo arm" was introduced on Fender guitars.

But the terms that became established were "tremolo arm" and "vibrato unit", both contrary to standard usage, with the result that electric guitarists traditionally use the terms "vibrato" and "tremolo" in the opposite senses to all other musicians when describing these hardware devices and the effects they produce.