King Charles III will mark his 78th birthday with an appearance on Sir Elton John's "Rocket Hour," joining the musician for an hour-long broadcast celebrating the artists and performances that have supported The King's Trust over five decades.

The Apple Music Radio special airs Saturday, Nov. 14, and will be available free throughout the weekend. Recorded last month at Apple Music Studios in London's Battersea Power Station, it combines musical selections with memories of fundraising concerts and discussions about helping young people build creative careers.

A preview shows the pair exchanging jokes about their age after Charles describes Elton as a "national treasure."

"I'll be on the Antiques Roadshow next," the singer replies.

"Join the club!" Charles responds, laughing.

The conversation centers on The King's Trust, which Charles founded in 1976 as The Prince's Trust. Now marking its 50th anniversary, the charity helps disadvantaged young people develop skills, find employment and start businesses.

Elton, a longstanding supporter, praised the King for maintaining that commitment while promoting music and the arts.

"The fact that you've done this and you continue to do it is an incredible feather in your cap and I congratulate you," he told Charles.

The full playlist will remain undisclosed until Saturday, but confirmed selections include Raye's "Joy," Skye Newman's "Hairdresser" and Muse's version of "Feeling Good." Buckingham Palace said the programme would span different decades and genres, with stories connecting many of the performers to the trust.

Muse received support to buy equipment when the group was performing under its earlier name, Rocket Baby Dolls. The band subsequently became a headline act at fundraising events for the charity.

Charles and Elton also revisit the Wembley Arena rock galas of the 1980s, where Elton performed, alongside events at the Royal Albert Hall and major concerts in Hyde Park. Elton has contributed a pair of his rose-tinted spectacles to the trust's 50th-anniversary auction.

Explaining his participation, Charles said the invitation offered a chance to recognize established supporters alongside musicians whose careers the charity had helped develop.

"Music has always been at the heart of The Prince's, and now The King's Trust," he said, describing the opportunity to select tracks as "an opportunity too good to resist."

The recording coincided with the pair's visit to launch Apple x King's Trust Creative Labs. The initiative provides young people with workshops, access to Apple technology and guidance from industry professionals to develop creative skills and explore employment opportunities.

It is Charles's second collaboration with Apple Music, following last year's "The King's Music Room," which featured 17 of his favorite songs. A Buckingham Palace spokesperson joked that finding another project presented the challenge of avoiding "the difficult second album."

During the new programme, Charles described the purpose behind the charity's work: "Well really, what I was trying to do was invest in the future, but particularly investing in talent."

"That's the greatest thing you can do," Elton replied. "Young people are our future, and you're doing a wonderful job."