Ray Charles In Country Comes Home (1981)

Clipping from Jet, 2 April 1981.

Country Comes Home was a CBS TV special, recorded on 1 April 1981, directed by Walter C. Miller, and aired on 10 April 1982. Most of the show was staged at the Grand Ole Opry, as a benefit for the Opry's Trust Fund. Johnny Cash opened with a song mentioning most of the performers. Ray gave "his definitive rendition" of Georgia On My Mind.
He also performed a gospel duet with Loretta Lynn. This is probably the performance that received "the standing ovation" mentioned here (sub Wish You Were Here Tonight).

Update 25 November 2013:
The website of the Country Music Hall Of Fame - surprisingly - offers a 30-second clip from the show. It indeed turns out to be a duet on a 'southern gospel' tune (written by Hank Williams): I'll Fly Away.

It was indeed a medley, with I'll Fly Away, Amazing Grace and an unidentified third gospel song:
   [Video was deleted from YouTube]

Off topic: also read this.