The following texts have been quoted from Wikipedia:
http://en.wikipedia.org/wiki/In_the_air_tonight

Released in January 1981 in the UK, the single was an instant hit, quickly climbing to #2 on the singles chart. It was also an international hit, reaching the top 20 on the Billboard magazine pop singles chart in the summer of 1981.

The recording is notable for its atmospheric production and macabre theme.

The lyrics of the song take the form of a dark monologue directed towards an unnamed, possibly prominent person; the singer describes having witnessed an unspecified act perpetrated:

"I was there and I saw what you did
saw it with my own two eyes"

and anticipating an equally unspecified consequence:

"I can feel it coming in the air tonight, oh Lord
I've been waiting for this moment for all my life"

Musically the song consists of a series of ominous chords played over a simple drum machine pattern (the Roland CR-78 Disco-2 pattern, plus some programming); processed electric guitar sounds and vocoded vocals on key words add additional atmosphere. The mood is one of restrained anger until the final chorus when an explosive burst of drums releases the musical tension, and the instrumentation builds to a thundering final chorus.

Collins wrote the song in the wake of a failing relationship with his then-wife. Collins has described obtaining the drum machine specifically to deal with these personal issues through songwriting, telling Mix magazine: "I had to start writing some of this music that was inside me."