Soundtrack found here

Sort of.

The soundtrack was never released on disc or tape anywhere.

But back in 1975, I stopped in at a Wherehouse store in California and found a stack of free "soundsheets" (flat flexible vinyl squares playable on turntables).
On it was Herbie Hancock demonstrating new features of the Fender Rhodes electric piano. It ends with this:

"We re-recorded it for our latest album. And we had a lot of fun doing it! Here's a short segment of the theme from 'The Spook Who Sat by the Door'".

That three-minute clip changed my life.

Because of it, I learned to love jazz. A pianist raised on classical, I had opened a Door to a whole new musical landscape. And a few years later, when I got my first component stereo, I thought it was time to upgrade my little worn soundsheet to the album of which Herbie spoke.

It didn't exist.

There was no internet back then, so I couldn't find out that the "latest album" Herbie referred was never released, as he was in a transition then from Warner Brothers to Columbia. A less-funky version called "Absolute Proof" did appear on his 1974 album "Thrust", but it's a far cry.

Two and a half decades later, in 2000, that very same "incredibly rare"
soundsheet appeared for the first time on the CD "The Soul of Science" on Obsessive Records. Not a very good transfer, but it's still a fabulous track. If you like this film's music you owe it to yourself to get your hands on it while it's still available.