A vibrato unit is an electronic effects unit used to add vibrato to the sound of an electric instrument, most often an electric guitar. Vibrato units may be individual stomp boxes or built into multi-effects units, but are traditionally built into guitar amplifiers. Vibrato units are particularly used in surf music.
The name vibrato unit is contrary to normal usage of the term vibrato, and in that sense the unit is incorrectly named.[1] The guitaring tradition of using the term "vibrato" to refer to a tremolo effect began in 1956 with Leo Fender's use of the term in naming the Fender Vibrolux. In all other contexts the effect produced by a traditional vibrato unit is known as tremolo rather than vibrato.
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.
In sales literature, Magna called the vibrato "F.M. Vibrato" for full modulation vibrato). Whereas most other companies incorrectly labeled volume modulation as vibrato, Magnatone's vibrato was true pitch shifting vibrato.