This legendary moment in rock history took place at the The Actuel Festival at
Mont de I'Enclus in Amougies, Belgium on October 25th, 1969.

Zappa was invited to the festival by organizer Pierre Lattès and turned out to be
something of an omnipresent force: MC-ing much of the festival, road managing
Captain Beefheart, and jamming not just with the Floyd but with Blossom Toes,
Archie Shepp, Beefheart and ace drummer Aynsley Dunbar (whom he would soon hire himself).

Frank is introduced (in French) midway through the set and joins the band on an
 extended 21-minute rendition of “Interstellar Overdrive”.


Nick Mason from a March 1973 interview:

“Frank Zappa is really one of those rare musicians that can play with us.

The little he did in Amougies was terribly correct.
 
But he's the exception.

Our music and the way we behave on stage, makes it very hard to improvise with us.”