Elvis sang a few lines during an informal recording jam at his home in Palm Springs in April 1974.
Lyrics by Carolyn Leigh.
Music by Johnny Richards.
Leigh’s lyrics were put to Richards’ instrumental ‘Moonbeam’.
Recorded by Frank Sinatra, 1953.
Released on 9 December 1953.
https://youtu.be/qc7EuqcRdYM
Sinatra's friend and frequent arranger Nelson Riddle introduced him to the song. "Nelson told me he had a song that had been floating around Vine Street [Capitol Records] and other companies for weeks or months," he recalled in Frank Sinatra: An American Legend. "'I think it's a good song,' Nelson said, 'but nobody wants to do it.' I didn't even ask him if I could hear it. I just said let's do it, and it turned out to be 'Young at Heart.' We did a single, and it was a big hit."
The single was so successful on the pop charts, peaking at #2, that the film Sinatra was working on with Doris Day was renamed Young at Heart. The song plays during the opening and closing credits.
Sources: Wiki - Songfacts - David Neale