King Charles and Sir Elton John joked about the problems of ageing as the pair joined for a special radio show to coincide with the monarch's 78th birthday.
Sir Elton, 79, was joined on his regular Rocket Hour radio show for a special episode during which the King shared his musical memories as the pair chose 14 songs together.
The programme also marked the 50th anniversary of the King's Trust and highlighted how musicians have supported the charity's efforts.
"We and the Trust are definitely still standing," the King said, as he highlighted Sir Elton's track I'm Still Standing as one of his favourites because of the song's "message of resilience".
The music legend joked in reply: "I'm still sitting now, though" giving a large laugh, with the King chuckling: "With occasional bits dropping off here and there. I know this is a terrible problem as we get older."
The special was recorded last month at Apple Music Studios in south London and premiered on Saturday morning.
The King recalled Sir Elton's 1986 performance at Wembley Arena, which marked the charity's 10th anniversary.
"I suspect that no-one who was present on that night in 1986 could possibly forget your performance of I'm Still Standing," King Charles said.
"I know people in all kinds of circumstances find this song inspiring, not only for its marvellous spirit, but also its message of resilience. And certainly, 40 years on from that remarkable concert, we and the Trust are definitely still standing."
The pair selected a total of 14 tracks. King Charles picked Giant by Calvin Harris and Rag'n'Bone Man, telling Sir Elton that the song summed up his charity because of its message of finding strength from others.
Also selected was Bob Dylan's Gotta Serve Somebody, Muse's Feeling Good and Nectar Woode's Wine into Water, which features Sir Elton on piano.
The Rocket Man star asked the King to highlight a song that he found "extremely meaningful".
Replying that there is "nothing more meaningful than love", the King described an "unforgettable performance" of The Beatles' 1967 hit All You Need is Love by Sir Paul McCartney in 2002 at a concert in honour of Queen Elizabeth II's Golden Jubilee.
"I shall never forget the magic of witnessing a simply unforgettable performance of All You Need Is Love for my late mother's Golden Jubilee at the Party At The Palace concert with Paul McCartney, Rod Stewart and Joe Cocker, and I think with Phil Collins on drums, Brian May and Eric Clapton on guitar and an all-star backing choir," the King said.
"It really is a totally timeless song with a timeless message."
The show opened with Tina Turner's hit Proud Mary. The King described the late pop icon as an "electrifying character" and recalled that the guard at Buckingham Palace played her hit Simply the Best following her death in 2023.
"It was, I hope, a small way of thanking her for the times she has performed for my charities and indeed for the joy she brought to millions of people," the King said.
The pair also chose Sir Rod Stewart's Handbags And Gladrags, Elvis Presley's Hound Dog, Pete Townsend's Let My Love Open The Door and Raye's Joy.
The programme will be rebroadcast on Apple Music One at 17:00 and 22:00 Saturday and again on Sunday at 02:00 and 06:00. It will also feature on Apple Music Hits on Sunday at 10:00 and 14:00.
