Sir Elton John says his new song with Stevie Wonder is "one of the greatest songs" he's ever written.

The 'Rocket Man' hitmaker and the 'Signed, Sealed, Delivered I’m Yours' singer - who have been friends for five decades - have released the track 'Finish Line' from the former's star-studded 'The Lockdown Sessions' LP, which is released on October 22.

The pair previously teamed up on a cover of 'That's What Friends Are For' with Dionne Warwick and Gladys Knight back in 1985.

And the 74-year-old music legend explained how the new duet - which is produced by Andrew Watt - happened entirely behind "accident", but turned out to be his one of his favourite tunes he's ever released.

Speaking to studio wizard Andrew on Elton's Rocket Hour on Apple Music 1, the 'Tiny Dancer' hitmaker said: "This track I did with Stevie Wonder is a very unusual way of writing. Usually, I write to lyrics, but I wrote the melody first in the studio, and then your girl put lyrics to it.

"And then Stevie came along and played piano. I played electric piano, and then he did harmonica on it. And then we were trying to get another vocalist on it and he wouldn't do it because I think he thought he'd done enough. And then you put the gospel choir on, Kanye West Gospel Choir on it.

"And I think when Stevie heard that he decided to do the vocal. And I think for me, it's one of the greatest records I've ever made. Because A, it's Stevie Wonder, and you made Stevie sound like a 17-year-old again. And the sheer joy in his voice, it was magical, magical, the way this thing came together was a series of accidents in a way.

"I'm so proud of this record because I love him so much. He's always been so kind to me and so sweet to me, the talent is beyond ridiculous.

"And it was just lovely to spend time with him and just see this wonderful human being smiling and happy and playing on a record of mine."

Speaking of the song, Stevie, 71, said Elton's "wisdom, pain, soul, love, and resilience" can be felt throughout.

He said: "It is both a joy and honor to sing, play piano and harmonica for Elton! He has truly been one of the great spirits of music, life, friendship and love, who I've met on this life journey! True artistry and music like love equals a forever commitment lasting many lifetimes. And Elton, anyone who hears your voice singing "Finish Line", will hear and feel your wisdom, your pain, your soul, your love, but also your resilience..... I love it!! Congratulations to you and our forever and never, never-ending music, friendship, life-song! Long live Sir Elton John!!! (big smiley face!) (sic)"

'The Lockdown Sessions' also features tracks with the likes of Brandi Carlile, Charlie Puth, Dua Lipa, Eddie Vedder, Gorillaz, Lil Nas X, Miley Cyrus, Nicki Minaj, Rina Sawayama, SG Lewis, Stevie Nicks, and Young Thug.

Tune in and listen to the episode in full this Saturday (02.10.21) at 5pm BST at apple.co/_RocketHour.