Atom Heart Mother has "If" – written by Roger Waters.

Yes. The track “If” appears on Pink Floyd’s 1970 album Atom Heart Mother, and it was written by Roger Waters.

Atom Heart Mother is their first album to reach No. 1 in the UK, but it’s also the one the band later called “a load of rubbish.” “If” is one of the quieter, acoustic moments on the record — classic early Waters, all melancholy and introspection. He sings it too.

If you’re digging into Pink Floyd’s deep cuts, this is a solid one. Not their best, but it shows Waters finding his voice before Dark Side made him a household name.