The Song
"In The Air Tonight" doesn't have a traditional song form by any means, but the form is understandable after you realize that it was more or less improvised. The form looks like this:
Intro, Chorus, Verse, Chorus, Verse, Chorus, Chorus, Chorus, Chorus,
The intro is interesting in that it's 20 bars long, with the first set up part at 12 bars, then 8 bars of the keyboard pad. Then it begins with a chorus instead of a verse. There's no bridge and the outchorus repeats against a very long fade.
The Arrangement
As unusual as the song form is, so is the arrangement. Many of the instruments used don't play the role that you're use to them playing, like the guitar, which is used mainly for sound effect fills. Here's what the arrangement elements look like:
* The Foundation: Drum machine throughout, drums (with no cymbals) on the last chorus.
* The Pad: Synthesizer
* The Rhythm: Pedal bass synth drone until the last chorus, when it changes to a reggae bass line that's doubled with a synth string line (very unusual), as well as a high synth pedal sound during the first and second chorus.
* The Lead: The lead vocal
* The Fills: Guitar effects, vocoder vocal at the beginning of the 2nd verse.
The Sound
"In The Air Tonight" was extremely influential for the sound of the ambience on the drums that was the result of the Listen Mic circuit on the SSL 4000 console, which is a sort of reverse talkback so the people in the control room can hear the musicians in the studio. The Listen Mic circuit has some heavy compression built into it so the level between musicians close or far away from the mic can be heard evenly, and this is what gave the drums the distinctive sound after the console was modified so you could record it. Producer/engineer Hugh Padgham later recreated the sound with heavily compressed and gated room mics, and that sound was eventually incorporated into most digital reverbs in what we know today as "Gated Reverb." This was the sound that engineers tried to emulate for a decade or so thereafter, as the gated reverb drum sound became very popular.
The song was built around a then new Roland CR-78 drum machine pattern (called "Disco 2"), which is bone dry and in your face, which represented the base layer of the ambience layers.
The synth pad, which is the most prominent instrument throughout the song, has a short delay (less than 100 milliseconds) that's panned to the right to give it a stereo soundfield, while the dry synth sound is panned to the left.
The lead vocal has a very distinctive sound also thanks to a short (less than 100 ms) delay and a touch of small room reverb. It's possible that it's the same delay that's on the synth pad. In the second chorus, a second longer 1/4 note delay is introduced at the end of each phrase. It also features an interesting use of a vocoder on the vocals during the second verse.
The Production
So many of the sounds are distinctive in this song, but the production really makes it a hit. While one might think that the synth carries the song on a passing listen, it's really the repeating synth bass drone and the high synth drone in the chorus that add motion. These two are down in the mix so it's easy not to be aware of them.
The other thing to notice is the fact of how the song develops, as most hits normally do. The second chorus introduces a harmony vocal with a long delay at the end of the phrases, the second verse introduces the vocal vocoder, and the last chorus and outro introduces the drums and bass line, which is doubled with a synth string sound. Collins then ad libs the lead vocal over the fade of the song. There's constantly something new happening throughout, even though it may be subtle, to keep your attention.
One last thing - although the sound of the real drums on this record would change drum sounds for a long while afterwards, the most interesting thing about them to me is that there are no cymbals ever played.
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