TL;DW: ADT is a double short delay tap with saturation.
ADT means ‘artificial double-tracking’. You could also call it fixed flanging. It’s a single short delay, as heard on lots of Beatles tracks. It’s now my job to explain what’s different about the Airwindows ADT, what you can do with it beyond the obvious ‘stick it on like a preset and pretend you are a Beatle’, and why you’d bother.
With the Airwindows ADT, you get two delay taps (making it A3T?) and an important feature: the mix sliders used to apply the delayed taps are ‘attenuverters’. That’s a word from Modular Synthesizer Land, which means you get both output level control and the ability to invert the output. Here’s why that matters.
If you apply a fixed delay tap, you get an effect called ‘comb filtering’ where you’re emphasizing and cancelling frequencies based on how long the delay is. You’d think that would sound really strange, but it’s the same way you hear a direct sound and also the sound bouncing off a floor or wall: we naturally hear through comb filtering rather well, which is why room design is important in studio control rooms. (you could have a bass frequency getting cancelled, be unable to hear it at all at your listening position, and yet things will still sound perfectly normal.) Applying a quick delay like this can make your sound richer and more textural, and a little more ambient. If it’s a very short delay it may not be heard as an echo at all.
But, if you’re using an INVERTED delay tap, something else happens: the shorter the delay and the closer to the volume of the dry signal, the more it’ll cancel out the bass. You’ll still get all the comb filtering effects, but you’ll also be removing lows, either the deep lows or even low midrange if the delay’s really short.
If you blend two taps that are both inverted, you can cut bass while averaging out the comb-filter effects. If the taps are in phase (not inverted) what you’re doing is reinforcing the bass, because the cancellation effects will run out below a certain frequency and just add together. All this is using very quick delays, though ADT lets you lengthen them to where they’re slapbacks. Don’t be too distracted by that, part of what makes ADT its own effect is the ability to shape the tone with delays too quick to hear as echoes.
Finally, now that you know you can cut bass using these very quick delays, or reinforce it, or any combination you like… there’s a headroom control. ADT will distort like crazy using low headroom. That can be used as a distortion effect… but it’s not just ordinary distortion, it’s a combination of Spiral into Console5’s buss (PurestConsole, for clarity and well-behavedness). These don’t perfectly cancel out. Instead, it produces a slightly leaned-out, skinnier tone to complement the way ADT fattens things up. If you’re using it to thin bass, it’ll be even more effective. If you’re reinforcing the body of the sound, it’ll color things in a subtle but interesting way. And of course if you love it, you can set up mixes that way (swap out Console5Channel for original Spiral, either on mix elements you’d like a little thinner and more energetic, or the whole thing). Sometimes there are new types of coloration that owe nothing to EQ or traditional processing: this is one of those times.
I’m supported in these experiments by Patreon, and that’s how I’m able to be still doing this every week. I’d like you to think of all these plugins as free, but pretend that some of the coolest ones are $50 to own forever (complete with source code and lifetime support). Sound reasonable-ish? Turns out that ‘the coolest plugins’, the ones that cost $50, are entirely up to you. If you find those ones you depend on and use like the forever-plugins they are, get on the Patreon and pledge the equivalent of $50 a year, or $100 if you depend on two, and so on. Then, next year, see if there are more. So long as I make at least one plugin a year that people love (doesn’t have to be the same one for everyone) then I can make as many as 52 for everyone to have, and there’s no reason they ever have to be taken away (that’s what open source is for: not only are they supported but you have recourse if Vermont gets hit by a giant meteor. Someone will be able to compile them, thanks to the Patreon-supported open source project that is Airwindows. That’s serious future-proofing)