PreSonus Blog

Authentic ADT (Automatic Double-Tracking)

Double-tracking is the process of recording the same part a second time, and trying to duplicate the original part as closely as possible. The goal is to make a part sound bigger, more prominent, or (with mono instruments), create a stereo image from the two tracks. 


Spoiler alert: humans aren’t perfect. When playing the second part, there will be slight timing, and perhaps pitch, variations. Within reason, these variations are good, because they keep the part from sounding like the original part was just copied to another track. However, sometimes it’s difficult to play a second part that’s tight enough, especially with something like a complex or fast lead guitar part. The usual solution is to do electronic doubling using an effect, like Studio One’s Chorus/Doubler.


However (at least to my ears), electronic doubling has never sounded quite the same as actually double-tracking a part. So here’s a different approach that I find more satisfying, and closer to “the real thing.” It requires copying the original track, processing it as described in this tip to create the doubled sound, then mixing the processed track with the original track. The audio example plays the original track, then the doubled version using this technique.




I wasn’t planning to do an effects chain, because the Analog Delay settings in Fig. 1 are pretty foolproof. In fact, unless you want to explore the options brought out to the control panel, just insert the FX Chain, and carry on with your mixing or recording.


Figure 1: Analog Delay settings for the Authentic ADT effect. 


How It Works


To give a more randomized effect, there are two delays (delayed sound only) in series, set for the same initial delay time, but modulated at different LFO rates. So the longest, and shortest, delays happen only when the maximum deviations of the two LFOs coincide. Otherwise, the delay changes constantly, in a somewhat non-periodic way. 


But the “secret sauce” is using this on a track dedicated solely to producing the ADT effect. One of the problems with electronic ADT is that the variations can never be ahead of the original, or at the same time—they can only lag. Real double-tracking doesn’t work that way. Sometimes the player will hit a little ahead, sometimes a little behind, and sometimes right on the beat.


To solve this issue, suppose your initial delay setting 20 ms, as in Fig. 1. Because there are two delays in series, this means the total initial delay setting is 40 ms. Move the copied, doubled track 40 ms ahead (earlier) on the timeline. Now the initial delay isn’t delayed compared to the original track, so as the delay time varies, it can lead or lag the original part. (Moving the doubled track ahead by 20 ms acts more like an electronic doubler, where the doubled part always lags, or plays at the same time as, the original.) 


Initial delay time settings of 13 to 25 ms work well. For whatever value you choose, move the original track ahead in time, compared to the original track, by twice the amount of the delay time setting.


The Macro Controls Panel


Fig. 2 shows the Macro controls panel. These parameters have been constrained to what I find to be useful settings.  


Figure 2: Control panel for the Authentic ADT FX chain.


The maximum delay is 25 ms because remember, there are two delays in series so this can go as high as 50 ms. If this amount of delay happened all the time it would be perceived more like slapback echo, but happening on occasion adds to the realism.


Depth and Rate are to taste. I generally adjust them to give a minimal flanging effect in case the original and doubled tracks end up being summed to mono at some point. However, that’s a worse-case scenario. This technique is designed for a cool stereo effect, with the original and ADT tracks panned oppositely (not necessarily full left and right, just oppositely). 


Mod Shape affects only one of the delays, but is interesting. A sawtooth shape, with the other delay being modulated by a sine wave, may give good results if the audio isn’t too continuous. Square can be useful with very low Width settings, but you’ll probably get more use out of sine or triangle wave modulation.


So go ahead—download the FX Chain! I think you’ll agree it gives a more authentic ADT sound.