"I was born in the same hospital in which Alexander Fleming discovered penicillin," he writes in his new memoir, "Unfaithful Music & Disappearing Ink" (Blue Rider Press). "I apologize in advance that I have not been the same boon to mankind."
The McManuses lived on a quiet street in London's Twickenham neighborhood. His mother worked in a record shop. His father, Ross McManus, was a singer and a trumpet player in a popular big band. In 1963, his dad played a royal command performance for the Queen Mother.
Also on the bill that night, "a little group from Liverpool called The Beatles," Costello recalled. "And my Dad brought home The Beatles' autographs for me. I glued 'em in my book."
Elvis was 14 when he saved up to buy his first guitar, from a store across the Thames River, in Richmond: "And then the day I got it, it was pretty great. I walked over with it over my shoulder."
"Back across the bridge?"
"Yeah! So yeah, 'I'm a musician now, you see?'" he laughed.
"You've talked about this whole idea of fluidity of identity," said Mason. "You have not had a problem sort of shifting your identity."
"This also goes back to my Dad."
To make extra cash, his father would sing as other artists on cheap knockoff records: "They would make note-for-note covers of current hits. And he would be Frank Bacon and the Baconeers, or Hal Prince and the Layabouts. So was it unusual to be called Elvis? Not if your Dad's Frank Bacon."
"You can be anybody."
"And have been!"
He's changed identities -- and writing partners, once working with Paul McCartney. "I thought it was a prank when I was told that Paul wanted me to come and write songs. But you don't turn up, you know, in your short trousers and your fan club card in your top pocket sticking out, you know? I mean, obviously you have to turn up responsibly with your guitar and a couple of ideas."
Costello had the beginnings of a song about his grandmother grappling with Alzheimer's. "So we made it, 'Veronica,' into a pop record that actually got onto the radio even though it's speaking about the unraveling of the mind."
A decade later, he collaborated with Burt Bacharach, beginning what has become a 20-year relationship. They're writing two musicals together.
"It's midnight and the phone rings, and it's Burt Bacharach: 'Elvis, where are the lyrics?' You know it's him driving it all the time, it's pretty great!" he laughed.
He jumps genres, from pop to classical to jazz. He once performed with an 80-piece orchestra at the Royal Albert Hall. That's where he once saw his future wife, jazz great Diana Krall, play one of his songs many years ago.
"I saw Diana play when we first friends. She played 'Almost Blue' as an encore. And I thought, 'Hmmmm.' That was pretty exciting."
"You had a pretty rowdy life when you were younger," said Mason. "When you got married again in 2003, did you put that all away?"
"I tried to put it away a bunch of times. I mean, to my shame I didn't succeed in staying true to my first wife, who I deeply love. She gave me that beautiful son. And Diana is very understanding of that.
"The rowdy's not gone away. But the rowdy's just focused on one person!" he laughed.