by Phil Taylor
Vibrato is a useful and engaging effect because it adds depth and movement to the sound of the guitar making it richer and more complex. What follows is a quick overview of the history of the development of electronic vibrato for electric guitar.
Mechanical rotary tremolo systems, including Leslie’s, are based on the Doppler-effect. Discovered by Austrian mathematician and physicist Christian Doppler (1803-1853) in the early nineteenth century, the Doppler-effect is the apparent variation in pitch that a stationary listener hears from a moving sound source. In practice, the loudness of the sound also appears to vary and it is this combination of frequency (vibrato) and amplitude (tremolo) modulation that give Leslie Speakers and other Doppler-effect systems their characteristic sound.