Elton John, Brandi Carlile share their working experience on 'Who Believes in Angels?'

They released its title track alongside a trailer documenting the creative process, reported People.

In the video, John explained the album "came at the end of the most amazing year" following his Goodbye Yellow Brick Road Tour, and he was looking "to do something different" and not "coast" in his career.

Carlile, a longtime fan of his, felt like a perfect collaborator. "When I met her I fell in love with her, and I just thought she had the most amazing voice. I knew I would find her inspiring, and I knew she would find me inspiring," said singer.

"I wanted this album to be special, but you can't guarantee when you go into the studio that something's going to be special," continued John, who faced hardship throughout the process. "Reality is I was exhausted, I had a lot of doubt, and I was a nightmare -- angry, I was tired, I was irritable," as per the outlet.

He recalled "tension in the studio" throughout the making of Who Believes in Angels?. He ripped up a sheet of music while working with producer Andrew Watt and threatened to leave.

"Elton is prone to moments of insecurity, especially where the stakes are high," said Carlile in the trailer. "There were times where I thought, 'Why does he want to do this? Why? Why is he going from Glastonbury to making an album with me?'"

John thought about the "other people involved" in the album, and he chose not to "abandon" the project. "And the fog started to lift," he said. "Finally, we all started to flow," reported People.

While they didn't have an "easy" time making the album, Carlile described the challenges as "a place where such great music came from."

John looked to "challenge" himself and said Carlile "really pushed me."

She noted, "We made an album that I think is spectacular for all the ages. My life has been taking me to this album the whole time."

He agreed: "For me, it's immaculate. This came out the way I wanted it to come out. This is one of the greatest musical experiences of my life."

Who Believes in Angels? is set for an April 4 release. The pair will promote the album with a one-night-only concert at the London Palladium on March 26, reported People. (ANI)