Seems like he used it for Lady Madonna, Back in the USSR, Why Don’t We Do It In The Road, and That Would Be Something, and then never used it again. It’s certainly the most distinct voice of his, at least when compared to all his other voices. I would’ve liked to see him use it more often.
Disagree...Oh Darling is a whole other voice......however, on the Abbey Road outtake of OD, he uses that high pitched voice which is also used in get Back/Winding Road and the backup vocals on 909 and Ballad Of John and Yoko.
As far as I know the only time Lennon crticised McCartney's singing was on a track of the Decca sessions ( can't remember which one ). He put down his songs on a number of occasions though as we all know.
It seems he only breaks out the "Fats" voice on special occasions in fairly recent times, like when he's actually evoking Fats, i.e. "Coquette."
Sorry, somehow I missed your post. Seemed like people couldn't find a use of that voice after 1975. In general, by the 80s it was all about tenor voicings - perhaps McCartney just saw it as old-fashioned by then?