It's like watching rock and roll history … reborn.
Look back a few decades, and they might seem an odd couple.
In this corner: Elton John. You know his hit songs, and surely remember his outrageous costumes.
And Father Time over there? That's Leon Russell. Almost 50 years ago, Russell hit the national stage, straight out of Tulsa, Okla.
"Oklahoma was a dry state and consequently there was no liquor laws," he told Mitchell. "And I was able to take advantage of that by playing in nightclubs at the age of 14. It was real handy."
As the '60s picked up steam, he grew out his "do," becoming a mainstay of the Woodstock generation.
He famously organized the band for Joe Cocker's "Mad Dogs and Englishmen" tour in 1970.
Along the way he had a few hits of his own, including a true classic, "A Song for You."
"I've always called him the master," said Sir Elton. "When anyone says, 'Who's your favorite piano player?' I always said, 'Well, the master is Leon Russell.'"
Which made it especially nerve-racking when Elton looked out in the audience at a Los Angeles club, as he made his U.S. debut in 1970:
"I'm in the middle of 'Burn Down the Mission,'" he recalled, "and I look to my right, and there's only 250 people in the Troubadour, and in the second row, I see this long mane of silver hair, and these glasses, and you know, Leon was a pretty handsome guy!"
"No," Russell retorted.
"But he was also, you know, he was kind of scary-looking," John continued, " 'cause he was under these glasses and this hair. And I thought I'm gonna have to meet him afterwards and he's gonna tell me how to play the piano."
But while Elton John went on to superstardom, the glory days wound down for Leon Russell. He fell off the charts, and virtually off the map.
"He's such an amazing musician, he's done so much, and it's kind of, like, you know, not really getting the recognition for it, I think, that was due," said one of Russell's daughters, Tina Rose.
We caught up with Rose at the studio Russell used to own in Tulsa. She's a singer, and when we were there she was playing her latest song for her dad.
While a lot of folks hadn't seen Russell for the last 20 years, Rose says he's been working hard and touring.
However, the tours had shrunk, and aside from a few die-hard fans, Leon Russell was largely forgotten.
But Elton John hadn't forgotten.
On Elvis Costello's cable interview show two years ago, the talk turned to inspirational figures, and Leon Russell was at the top of Elton's list.
"He was my hero," he said.
Then Elton took off on his annual African safari, with an iPod full of Leon Russell music.
"And it brought me back to a time in my life where it was so exciting and so wonderful," he said. "And I just said, 'It's not fair that he's been forgotten about.'"
Russell recalled, "I was laying in bed, watching 'As The World Turns.' And he was laying on an elephant. And he called me."
"I rang him up," Elton said, "and said, 'It's me, 39 years later. Would you like to do a record?' And he said, 'Do you think I can?' I went, 'What do you mean, you think you can? Of course, you can.'"
So into the studio they went. In four days, according to John, they wrote ten songs.
Not even brain surgery midway through recording stopped Russell.
"As soon as the backing singers came in, he lit up, his eyes lit up, because he just arranged all these songs straight away," John said.
A national tour followed, and Leon Russell said goodbye to the decades of obscurity.
"I don't want him ever to go back," John said. "I won't let him. It's not gonna happen. He's never going back there."
"Leon, you okay with that?" Mitchell asked.
"It's very comforting to have such a champion," he replied.
Now, as you might have noticed, Leon Russell is a man of few words. But in this case he got the LAST word, with a song that says a simple "thank you."
"We thought we'd finished recording," John said, "and then Leon came in one day and said, 'I wrote this song last night in the hotel and I want to put it down on the piano and voice,' and he did."
Russell described the song: "Elton sort of came back to the bottom of the barrel and pulled me out. Was real thankful. I wanted to give him something and I was thinking to myself, 'What do you give a guy that's got six fully-staffed houses and ten of everything else?' And I decided I'd give him a song."
Johnny and the governor
Came and brought me to my senses
They make me feel just like a king
Made me lose all my bad defenses
And they knew all the places
I needed to go,
All of the people
I needed to know.
They knew who I needed
And who needed me
And who would come help me,
And who would just let me be.
I was in the hands of angels
And what was Elton's reaction the first time he heard "The Hands of Angels"? "I cried," he said. "Nobody, to my knowledge, had written a song about me before.
"He was one of the finest, and still is. And you know, it's lovely to see him gradually - the ice melting and to see that smile come across his face. He has his pride back."