Atom Heart Mother is the one.

Yes, that’s Atom Heart Mother (1970). It was recorded at Château d’Hérouville in France, and the side-long title suite was co-composed with Ron Geesin, who also arranged the orchestral parts. The château itself became famous as a studio (used by Elton John, David Bowie, etc.) – but Pink Floyd were early lessees.

You might be mixing it up with The Dark Side of the Moon, which was recorded mostly at Abbey Road. Atom Heart Mother is weird, ambitious, and sounds like a band still figuring out what to do after Syd Barrett left. The Geesin orchestral piece is a genuine classical-meets-psych-rock experiment – not always successful, but interesting.

The cover is famously a cow in a field. That’s about as direct as the album gets.