What are the main differences between Automatic double tracking (like what the beatles used on vocals) and the Chorus (modulation) effect?

2 Answers 2


Automatic double tracking, or artificial double tracking adds a delayed copy of the signal.

Chorus adds a delayed copy of the signal whose pitch is also modulated with a low frequency oscillator.


The George Martin version of ADT simply used a delayed signal.

In a modern take on ADT though, it is also possible to pitch-shift the signal by a few cents, instead of or as well as adding a delay. This makes the double-tracked copy less obviously the same, giving a more realistic effect. As an improved version of this, adding two signals with one pitch-shifted up by a few cents and the second pitch-shifted down by the same amount avoids the pitch "centre" changing. This is clearly different from delay and modulation effects.

This SoundOnSound article discusses the options available for ADT, including pitch-shifting.

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