Perhaps two of the most used modulation effects by guitarists, chorus and flangers delay the instrument's signal by milliseconds while modulating the delay time at a constant rate. The modulated signal is then mixed with the original dry instrument to create the effect.

Chorus is named so because of the doubling effect it produces, making it sound like multiple guitars are being played. What does chorus sound like? Think The Police.

Phase shifters do exactly what their name implies: they shift the phase of the waveform from your instrument then mix the phase shifted signal with the original dry instrument. The amount of phase shift is modulated to bring the effect to life. The end result is a notch filter, with multiple notches, that move through the frequency spectrum in sync with the modulation rate. The effect can produce subtle to over the top modulation depending on the feedback or color setting.

We don't know how John Lennon came up with the name Flanger but thankfully he did because it perfectly describes the sound, from the famous jet engine effect to otherworldly modulation to subtle liquid effects. Flangers are not just used on guitars but just about every instrument in the studio from pianos to drum kits to stereo mixes.