Not invented, right (but I didn't say exactly that). However in the context of Sgt. Peppers:
According to David Fricke, the album was a major influence on The Beatles' Sgt. Pepper's Lonely Hearts Club Band. Paul McCartney regarded Sgt. Pepper's Lonely Hearts Club Band as The Beatles' Freak Out!
from Wikipedia
Re:How the Beatles Wrote ‘A Day in the Life’
by ZenoArrow on Monday May 22, 2017 @12:05PM
(#14394671)
Okay, but I'd say there were probably multiple major influences. Pet Sounds is also meant to be a major influence on Sgt. Peppers:
https://www.quora.com/How-did-The-Beach-Boys-Pet-Sounds-infl...
Re:How the Beatles Wrote ‘A Day in the Life’
by grasshopperpurp on Monday May 22, 2017 @02:19PM
(#14395776)
It came out in '67, so it wouldn't have influenced Sgt. Peppers, but I read that John Lennon had like 10 copies of Beefheart's Safe as Milk (Ry Cooder played guitar on that one).
Zappa did some amazing stuff, but he didn't invent psychedelic rock. Can read more about the early history here:
https://en.wikipedia.org/wiki/Acid_rock