Release Me (With Engelbert Humperdinck)

Unreleased.

When Ray guested in The Engelbert Humperdinck Show, recorded on 9 February 1970 in London, he an the host did a duet on the song.
He returned the favor 13 years later, when he invited Humperdinck to sing the same duet at A Man And His Soul, A 40th Anniversary Celebration, taped at the Cocoanut Grove club in LA in the early summer of 1983.

The '83 duet:


Live:
'70 TV Humperdinck
'83 TV Man

Ray Charles Ft. In The Engelbert Humperdinck Show (1970)

Photo: Alamy.

Ray appeared in the 7th show of the first season of The Engelbert Humperdinck Show, taped on 9 February 1970 by London Weekend Television, and first aired on 4 March 1970. Source here.
The other guests were Jerry Lee Lewis, Lulu and Marilyn Michaels. At 10:24:40 there's a brief snatch of Georgia, followed by Engelbert's introduction of Ray Charles, who then plays:

• Georgia On My Mind [partial; my conjecture, BS] 
• Let The Good Times Roll
• The Sun Died
• Makin' Whoopee (with Engelbert Humperdinck)

Probably after that, they did the duet on Release Me. Also read this.