ADT stands for Automatic Double Tracking, and it’s one of the many “secret sauces” of a great vocal track. I’d like to demystify this sound, and show you how to get it.
By the way, just because it’s the old school method doesn’t mean don’t do it. This method sounds great, and is fairly easy to achieve. Just record your vocals once, then make a new track and record them again. Even the best singers can’t robotically sing the same exact way twice, so there are going to be differences between the two tracks. Play them back simultaneously and you’ll hear a fat, thick vocal that may remind you of an old Beatles track. Well done (by the way, this is not ADT as it was not ‘automatic.’)
The Automatic comes in actually due to John Lennon. He HATED doing double tracking, as he found it difficult to sing perfectly twice and stay on pitch and rhythm. He asked his engineers to come up with a way to automate the process using the effects modules of the day.
Basically, the original track would be recorded onto a regular tape machine and a modified tape machine simultaneously. The second machine had a variable speed motor that slightly changed speed at a given interval. This made the mix sound like it had the natural imperfections of a true double track recording.
***Shiny New Digital Method***
Nowadays, ADT plugins are available to buy for most DAW programs. If you feel like rolling your own though, here’s a starting point:
Step one: make two copies of your vocal track
Step two: set sample delay on the second track, and randomly automate the delay time between 0-200 milliseconds
Step three: apply pitch correction to the first vocal track (don’t apply it to the second)
Now try playing it. You’ll get something very close to actual doubletracking without having to call the singer back into the studio, and you’ll be able to explain to your friends how clever of a mix engineer you are to boot!