Tremolo, in electronics, is the variation in amplitude of sound achieved through electronic means, sometimes mistakenly called vibrato, and producing a sound somewhat reminiscent of flanging, referred to as an "underwater effect".
History
The first self-standing electronic tremolo effects unit may have been produced by
Harry DeArmond, in which a motor shakes a canister containing a "hydro-fluid" (not mercury as some people assume), oscillating the canister containing an electrolytic fluid that sends the signal to ground. Earliest references to DeArmond's tremolo unit date to 1941.
[Presto Music Times, August 1941] Starting in the 1950s many companies began incorporating the effect into
, including the Fender Tremolux and Vibrolux:
Leo Fender marked the effect on Fender amplifiers as "vibrato", conversely calling the vibrato arm on his Fender Stratocaster a tremolo arm.
The most notable early amplifiers with built-in tremolo functions were the 1961
Fender Princeton and the
Gibson Falcon. In such amplifiers, the tremolo circuit was relatively simple, using as little as a dozen components and one half of a
Vacuum tube of the
Preamplifier. The effect was achieved through "bias wiggle", in which the
Grid bias of a tube, in the preamp or output stage, was
Oscillation (turned off and on, or partly off and on) in a pure
sine wave. Such circuits typically had controls for speed and depth, and produced an effect described as "lush, warm, and roundly pulsing".
Later amplifiers, and particularly the Fender Blackface amps of the mid 1960s and the later Silverface amps, used a much more complex circuit, producing the kind of effect that was especially popular with . Modulation was produced using an Opto-isolator, a light-dependent resistor whose pulsating signal (producing a lopsided wave) affects the preamp circuit.
