Automatic Double Tracking

Sobre la popular técnica de ADT en el disco Revolver de The Beatles en el fórum Gearsluts:

I was curious about the Beatles use of ADT (automatic double tracking) on Revolver. Lennon loved it as it meant he no longer had to sing twice to have the double tracked sound. On many songs, the original vocal and ADT'd vocal are mixed together "like "Taxman". But on some songs, like "And Your Bird Can Sing", and "Dr. Robert", they are panned hard left and hard right. So I imported the songs into Pro Tools, and set upon finding out the amount of delay by running a ddl on one side. It turns out the number is approximately 29.4ms. I can't say exactly. I did try to phase reverse one side and get it to cancel, but it wouldn't. Probably because they don't sound exactly the same, as one has another tape generation on it. Anyway, if you ever wondered how much delay ADT produced, now you know.