For your consideration, this is a clip from Frank Zappa’s unbearably fantastic live album, The Best Band You Never Heard In Your Life.
In particular it’s from a The Torture Never Stops > Lonesome Cowboy Burt > The Torture Never Stops jam fiesta on disc two.
There are two brief segments of Frank, sans music, making gutteral noises that are eerily similar to GELFspeak. Of course, this recording was made in 1988 and GELFs didn’t “really” speak like this until series VI…but both Rob and Doug are well-documented Zappa fans (Rob having claimed in an interview to have flown himself to San Francisco to see Zappa only to have Frank cancel the show due to illness, and Doug, as we all know, has named his dog Moon Unit…not to mention the fact that the initial version of “Om” was written to very same melody as Frank’s “Muffin Man”)…so who knows?
Hear Zappa speaking GELF