Frank Zappa (right) shares the stage with Pink Floyd's David Gilmour in 1969.

For five days in October 1969, Amougies, Belgium, played host to the Actuel Festival, an open-air music fest. Acts included Pink Floyd, Yes, Ten Years After, the Pretty Things, Keith Relf's Renaissance, Captain Beefheart and a horde of bands you've probably never heard of.

Bringing a bonus layer of weird to the event was its master of ceremonies, the one and only Frank Zappa.

"That was after the Mothers [of Invention] had broken up, and y'know, I had time on my hands," Zappa said several years later. "These people contacted me. They offered me $10,000 to be an emcee at a festival, all expenses paid, and go over there, and, y'know, whatever I wanted to do, and I said, 'Fine.' So, I get there, and they neglected to tell me that nobody spoke English."

They did, however, speak the international language of music (sorry, that was corny)—so Zappa made a point of jamming with several acts on the bill, including Aynsley Dunbar and Pink Floyd. Oddly enough, even though the video below shows Zappa on stage with Roger Waters, David Gilmour and the rest of Pink Floyd, Zappa had no recollection of the jam session. It must've been one hell of a music fest.

Interviewer: [You] performed onstage with Pink Floyd. True or false?

Zappa: Not with Pink Floyd.

...and...

To nail that down once and for all, you did not perform with Pink Floyd, right?

No.

Well, he did. Below, check out Pink Floyd and Zappa jamming their way through an extended version of the former's "Interstellar Overdrive," a brilliant tune from 1967's The Piper at the Gates of Dawn.

Pink Floyd drummer Nick Mason said in 1973, “Zappa is really one of those rare musicians that can play with us. The little he did in Amougies was terribly correct.” See for yourself.