The ADT technique was developed at Abbey Road Studios by engineers recording the Beatles in the 1960s. To free John Lennon from having to sing everything twice for real double tracking they came up with an artificial replacement: they sent the original signal to another tape machine and re-recorded it. Due to the physical distance between record and playback heads the new signal was delayed. The length of the delay depends on the tape speed (the slower the tape is running the longer it takes for the signal to travel from the record to the playback head). However, due to the machine’s (small amounts of) Wow and Flutter the delay time was not fixed but varied slightly, giving an additional chorus-like effect.
The ADT Plug-In takes a mono input signal and creates a stereo output. The original input signal will be output on one channel, the new ADT signal on the other. Blending the two is also possible.
My opinion ? I use only few freeware plugin effects – mostly I just use Ableton internal plugins. But thanks to ADT plugin I don’t need to clone and pan / delay channels for stereo effect. It’s very easy to use and works great as preview (and of course as final effect too). It’s definitely one of my favourite freeware plugins – I use it almost in every project – works both for vocals and instruments. ADT just improves my workflow nicely.
ps. There’s also AU version for Mac users.
Download: ADT – Artificial Double Tracking