Saw this on Pumpkinrot's blog awhile back and couldn't get it out of my head. Still one of the very best themes that John Carpenter and Alan Howarth ever produced. Here's what Howarth had to say about the process:
"The music style of John Carpenter and myself has further evolved in this film soundtrack by working exclusively with synthesizers to produce our music. This has led to a certain procedural routine. The film is first transferred to a time coded video tape and synchronized to a 24 track master audio recorder; then while watching the film we compose the music to these visual images. The entire process goes quite rapidly and has "instant gratification," allowing us to evaluate the score in synch to the picture. This is quite an invaluable asset."