Okay, now I'm barely understanding theory myself, but I'm willing to share some of the ways I create atmosphere in a track like the one above.
ggehiere and captnnrg both shared a couple of good creative ways to add some atmosphere, too. Check the original 'No more theory?' thread for those.
Adding reverb to individual sounds is a simple one. However, you have to take into consideration what instrument(s) you're going to do it to, and how much reverb (and what kind) to add. Those of you who get into programming your synths should carry that over into programming your own 'verbs, too. Most of the stuff I usually do has few if any beats or distinguishable rhythms (the track in the link ISN'T my usual forte), but most of this can be applied to more driving material as well.
So, find a sound or two, 'noises' or special FX work really well for this sort of thing, but a soloing piano or similar will also do nicely. You generally don't want this to be your 'mainline' but usually an accent or 'fluff.' Now apply a fairly heavy verb to the sound, a good deep hall, or, if you're programming your own, set up a huge space, make the verb very diffuse, a moderate amount of early reflection, circular or oval in shape if you have the option, and give it an 'average' of about two measures of decay. I say four measures worth, because the effect will generally sound best if it's 'tied' to the tempo of the song in some fashion. I say 'average' because you're going to want a couple applications of the verb at half (or even less) the length of your average decay, and a couple at twice (or more than) the average.
Now, mix your wet/dry ratio around until you get the verb thick enough on that sound to 'fuzzy' the edges of the sound. It still wants to be clear, but a small sacrifice of articulation is alright for our purposes. Apply our three verbs (short average and long) to particular sections of your track. Example:
Just before a short break in a track, use the short verb to sort of spill over ever so slightly into the break. It makes the break have a sense of 'coming at you' (you can also apply a verb to the whole mix - do it on a seperate track and mix the two to taste. In that case make the decay on the verb short enough to 'die' by halfway through the short break), especially if you slam out of the break.
Add a long verb application just before a long breakdown. As the break comes in, the decay of the long verb will leave the ghost of the prebreakdown floating into the pads.
Use the average verb application for select spots in your main sections (but still only on a few instruments). It'll add a sense of multilayered depth. Do this judiciously as you can kill a track's punch if you overdo it, but done right, you'll actually accent the punch.
You can also add some atmosphere to a track by appliying careful reverb and delay to your cymbals and snares. Delay is often used to give a boost to the hat rhythms, and a little subtle verb can often make hats sparkle with a little 'ghost' air. Snares can add some ambience with a little FX treatment too. Gated verbs work really well for making a spacy snare sound. Although a lot of folks think it's terrible, you can use a verb on the bassdrum sometimes to really cool effect (IMO). On the track above, I use a smidgen of verb on the first beat of the kick drum in certain areas to give it a 'boooom' kind of effect.
Now dunna overdo this, as you'll quickly end up having 'mush mix' if you don't use verb judiciously. And don't be afraid to experiment. The key, especially at the mixdown stage, is objectivity. It doesn't really matter if you've created the 'coolest verb on the planet' if the track doesn't need it, don't use it. Don't look at the track as your own at this stage (I know, impossible, but just keep it in mind), but as just 'a' track you're hearing. Keep your ear on the big picture, keep your attention on how the track sounds. Details should already have been taken care of at this stage, and if they haven't go back and do so. You don't want to have to think about 'oh I'll fix that sound in a mix' this is the mix. If a sound is fucked, fix it beforehand if at all possible. You can't 'fix it' in the mix, only hide it.
Anyhow, a couple more FX 'quickies.' Delay, she's a wondeful thing. I overuse the fuck out of it. Reverb will add space, but delay can add a whole other dimension of relections. Usually you'll want to apply delay prior to a reverb, or seperate from it (i.e., two different FX sends), but you can get some neat fx by applying delay to a 100% wet reverb signal, too. If you've ever had one of those old analog delays with the feedback knobs, you know how easy it can be to create a soundscape using nothing more than a single sound and the delay depth and feedback. If you can keep it under control you can make an entire sonic tapestry from that alone.
Synthesis: this one should be a no-brainer for those of you who already program your own sounds. With nothing more than the ADSR controls, you can simulate space and depth pretty easily. The difference in a 'sense of space' to almost any sound by rolling off the attack a bit, adding a healthy decay, long sustain and long release is usually pretty apparent. As Pongoid pointed out elsewhere, simply slowing down an LFO is a quick and easy way to get pad like sounds started. If you get in there and start detuning your oscillators, using Poly and Unison modes to layer sounds (if you have it available), toying with every available envelope setting you have, etc., etc., you'll quckly hear ways of adding more depth to some sounds. You can make synthesis really help out with the atmospheric side of things. Also, it usually sounds more 'lush' to sculpt the 'sound' than to simply drown a track in delay and reverb. Things stay more articulate too.
Adding silence. Silence is an excellent 'setup.' By going quiet (adding silence) just before something loud, it creates the illusion that the sound is actually much louder and more powerful than it actually is. The 'turnaround' break is an example. You're building, building, building, then just before you 'give it up' you drop most everything out, then slam the hammer down. You can apply the same technique to any part of a track you want a subtle 'boost' in. Create a volume envelope so that you do a minor fade of .25 - 1db over the course of 4-8 measures before the part you want to accent, then 'jack it' back to normal very steeply, but not too steeply. You want enough of your 'fade in' to give it a sense of swelling ever so slightly. At the amounts suggested, it should be subtle, that's the idea. Exaggerate the numbers to hear what I'm talking about to hear the effect more clearly. Do remember, it's supposed to be subtle, otherwise your mix will sound like it just got nailed by a compressor...
And speaking of compression. To add atmosphere, or keep it, generally stay away from compression. Compression kills a dynamic rage to some degree, and ambience is all about space. If you have to use compression, do it sparingly and only on the parts that actually need it. If you can, use a muti band compressor so you only compress those frequencies you actually have to. In the track on me site, those drums are compressed to hell, but mainly just from around 250-300hz down, there's a little notch at about 690hz that's got some strong compression, but all the main mids and highs went unmolested which helped to keep something of a sense of space with the drums.
Panning. Work your panning of various tracks, fiddle with the levels. A lot of time you can simulate depth AND keep things clear just by careful panning and level adjustment. Ever notice how anything mono never sounds as spacious as it does in stereo? Use that stereo field to your advantage. Don't just simply pan everything hard left and right. Give 'em a space. Just as you try and give each instrument or sound it's own frequency range to cover, fill up your stereo space just as carefully. Don't just pan cos it's fun (although I admit, I do it all the time), try and have a purpose to your panning. Although sometimes, like in the non rhythmic stuff I do, you can achieve a wonderful sense of disorientation by using LFOs of various rates and shapes to pan individual synth sounds.
Also, with relation to panning and depth. You can simulate something 'circling' the listener by using your pan controls in conjunction with your volume faders. For this example, pan right keeping the volume pretty much level until about 2 o'clock, then give it a tiny swell in volume as it goes between 2 and 4, then give a quick abrupt drop in volume right after 4 o'clock, continue to gradually drop the volume as you pan back left (and pan back a bit quicker as we hear mostly mono from behind depending on reflecting surfaces...), when you reach center you should be at your lowest volume, now gradually bring it back up as you pan left to 10 o'clock (but continue the 'faster' pan speed), again quickly notch the volume a bit as you pass 10 or so, then maintain volume as you approach center again. It sounds lopsided in print, but if you think about it, it really isn't given the nature of how we hear sound. If you want to accent this even more realistically, give a moderate high shelf cut to your eq at the volume 'cut' from about 7khz upwards, and keep that cut until you get to the volume notch, then let the eq return to normal. Why? Our high frequency hearing drops markedly once a sound moves beyond the plane of our ear canal (usually about a 45 degree angle or less from the ear toward the back of the head).
All the above numbers are relative to your kit. They're just some starting points so experiment to find out what suits the needs of a track. I'm also bettin' there's a lot easier ways to do what I'm sayin' and there's certainly a plethora of ways to simulate atmosphere using nothing more than volume contols. But there's a few things I could think of. Hope some of you find it useful in some fashion.
I'll sit down and try to do a thread about soundscapes at some point, just cos I like the damn things, AND I'm always looking for new ideas for mucking about with sound in general. So it should be cool to hear what some of you all do.
If you want to hear an example of my use of the more atmospheric stuff OUTSIDE the context of dance music, check me bits on Besonic or mp3.com
http://www.besonic.com/Mindspawn
http://www.mp3.com/mindspawn
Peace All