Tremolo

Tremolo pedal
Tremolo is an effect that creates a change in volume. It’s a so-called modulation effect that rhythmically changes the volume of your guitar signal. The way this is done differs. Every pedal has at least one low-frequency oscillator (LFO). This creates a waveform that turns the volume of the signal up and down.

Classical tremolos usually have sine or triangle waves. Sine waves provide a luscious effect. A triangle wave, with its straight and linear rise and fall creates an angular effect.

The effect has become popular because it was present in the first Fender amplifiers. This optical circuit uses a light-dependent resistor called an “optocoupler”. Also referred to as a “photocell”. This turns a light bulb on and off.

Today, almost every pedal has multiple waveforms available. Some pedals have the same optical circuitry found in many vintage amps. With this you can create different kinds of classic tremolo effects. In addition, with a tremolo pedal it is possible to use advanced waveforms not found on vintage amps.

Harmonic tremolo
In addition to the classical effect some pedals also have harmonic tremolo. This is an effect that splits the incoming signal into low and high. These two parts are then treated separately, producing strange, ‘phaser-like’ effects. It nearly sounds as an uni-vibe or similar modulation effects. So this is one to look for if you are into this type of vintage sound. Not every pedal has this option, so look for it closely if you want one.