The years-long artistic partnership between Tony Bennett and Lady Gaga wasn't an immediately obvious one.

Gaga was best known in the 2010s for pop hits like "Poker Face" and avant-garde experimentation on albums like "Artpop," and Bennett, a singer who mostly stuck to standards, was in his 80s when the pair met.

And yet Bennett and Gaga became fast friends and close collaborators, which they remained until Bennett's death at 96 on Friday. They recorded two albums together, 2014's "Cheek to Cheek" and 2021's "Love for Sale," which both won Grammys for best traditional pop vocal album.

"Tony is one of my most favorite people on the whole planet, and I love him with all my heart," Gaga told BBC Radio 2's Zoe Ball in 2021. "I can't tell you how much I learned from him, and what it's like to sing with a legend for so many years."

Bennett, who often referred to Gaga as "Lady," praised her talent and friendship over the years, too. And he loved Gaga for who she was, with her penchant for extravagant costumes and towering wigs.

"When I came into this with Tony, he didn't say, 'You've got to take off all the crazy outfits and just sing,'" she told Parade in 2014. "He said, 'Be yourself.'"

Gaga has not yet publicly commented on Bennett's death. CNN has reached out to representatives for Gaga.

When Tony met Gaga

In 2011, Gaga performed a Nat King Cole song at a fundraiser for the Robin Hood Foundation. Bennett was in attendance, and her performance so impressed Bennett that the crooner, whom she'd never met before, suggested the pair record an album together, she told Vogue in 2014.

"It's a completely humbling experience to be doing this with Tony," she said.

After releasing their first single together, the Rodgers and Hart hit "The Lady is a Tramp," in 2011, they started planning what would become their first album -- "Cheek to Cheek." The 2014 record included jazz standards by Cole Porter, Irving Berlin and those songwriters' contemporaries. In an interview with PBS, Gaga called it the "most important album of her career."

"Watching Tony at 88 like he's just starting out ... I said to myself, I can do this forever," Gaga told PBS in 2014. "Because he did it, and I really love him, and if I do it just like Tony, I'm going to do it right."

Bennett lauded her in return, calling her a "magnificent jazz artist."

"Either you got it, and that's the gift, or you haven't got it. And you've got it," he told Gaga during their PBS interview. "And you should spend the rest of your life just being yourself, and it'll excite everybody every time you ever perform."

Tony helped Gaga reclaim her voice

Gaga and Bennett recorded "Cheek to Cheek" after Gaga's 2013 album "Artpop" disappointed some critics and listeners. It was a difficult time for the artist, who was also recovering from hip surgery and enduring chronic pain from fibromyalgia. Working with Bennett helped her reclaim her voice, she said.

"I felt dead," she told Parade in 2014. "And then I spent a lot of time with Tony. He wanted nothing but my friendship and my voice."

Bennett convinced Gaga to keep performing, she said. He often shared advice he credited to Duke Ellington: "Number one -- don't quit. Number two -- listen to number one."

"Six months ago I didn't even want to sing anymore," she said. "I tell Tony every day that he saved my life."

Gaga supported Bennett through his Alzheimer's diagnosis

In between Gaga's next two solo albums, 2016's "Joanne" and 2020's "Chromatica," Gaga and Bennett recorded a second album of Porter standards, "Love for Sale," though it wasn't released until 2021. It was recorded after Bennett had been diagnosed with Alzheimer's, which his family didn't reveal until 2021.

Even after his Alzheimer's diagnosis, Bennett continued to perform, appearing with Gaga at Radio City Music Hall in 2021 in support of "Love for Sale." Gaga said she wasn't sure, during rehearsals, whether Bennett remembered her name. But performing still came naturally to him, she said, and he hardly missed a lyric.

"When that music comes on -- something happens to him," Gaga told "60 Minutes" in 2022. "He knows exactly what he's doing."

During the concert, when they took the stage together, Bennett unexpectedly introduced her by name. It was the first time he'd said her name in a "long time," Gaga said.

"When I walked out on that stage, and he said, 'It's Lady Gaga,' my friend saw me," she told 60 Minutes. "And it was very special."

Gaga escorted him offstage, his arm in hers, after his final public performance and their final night singing together.

"It's not a sad story," Gaga said of watching Bennett's experience with Alzheimer's. "I think he really pushed through something to give the world the gift of knowing that things can change and you can still be magnificent."