These two friends have sadly sung their last duet. 

Lady Gaga is mourning the loss of her friend and collaborator Tony Bennett, who died on July 21 at the age of 96. 

"I will miss my friend forever," Gaga began her July 31 Instagram message. "I will miss singing with him, recording with him, talking with him, being on stage together."

"With Tony, I got to live my life in a time warp," she continued. "Tony & I had this magical power. We transported ourselves to another era, modernized the music together, & gave it all new life as a singing duo. But it wasnt an act. Our relationship was very real."

Gaga noted that, in addition to teaching her about music and showbiz, he also encouraged her to keep her "spirits high and my head screwed on straight."

"He was an optimist, he believed in quality work AND quality life," Gaga shared. "Plus, there was the gratitude...Tony was always grateful. He served in WWII, marched with Martin Luther King Jr., and sang jazz with the greatest singers and players in the world."

"I've been grieving the loss of Tony for a long time," she wrote of Bennett, who was diagnosed with Alzheimer's disease in 2016. "We had a very long and powerful goodbye."

The 37-year-old also shared that, despite their 59-year age gap, Bennett really was her friend.

"My real true friend. Our age difference didn't matter-- in fact, it gave us each something neither of us had with most people," she added. "We were from two different stages in life entirely--inspired."

"Losing Tony to Alzheimer's has been painful but it was also really beautiful," Gaga wrote of Bennett. "An era of memory loss is such a sacred time in a persons life. There's such a feeling of vulnerability and a desire to preserve dignity. All I wanted was for Tony to remember how much I loved him and how grateful I was to have him in my life. But, as that faded slowly I knew deep down he was sharing with me the most vulnerable moment in his life that he could--being willing to sing with me when his nature was changing so deeply."

Gaga noted that she'll never forget this experience or her time with Bennett.

"If I could say anything to the world about this I would say don't discount your elders, don't leave them behind when things change," she wrote. "Don't flinch when you feel sad, just keep going straight ahead, sadness is part of it. Take care of your elders and I promise you will learn something special. Maybe even magical. And pay attention to silence—some of my musical partner and I's most meaningful exchanges were with no melody at all."

Gaga concluded with a message to her friend, "I love you Tony. Love, Lady."

The two musicians collaborated for over a decade, with Gaga first appearing on Bennett's 2011 album Duets II. After that, they released their joint album Cheek to Cheek in 2014, Love for Sale in 2021 and, that same year, hosted two performances together at Radio City in 2021 in honor of Bennett's 95th birthday. The two shows aired on CBS as part of the One Last Time: An Evening With Tony Bennett and Lady Gaga special. 

Over the years, Gaga has detailed how Bennett helped her career, giving her inspiration and motivation in a time when she thought was ready to leave music behind. 

Before working with Bennett, "I couldn't sleep," she told Parade Magazine in 2014. "I felt dead. And then I spent a lot of time with Tony. He wanted nothing but my friendship and my voice. The other day, Tony said, ‘I've never once in my career not wanted to do this. Six months ago, I didn't feel that way. I tell Tony every day that he saved my life."

Following his Alzheimer's diagnosis, Gaga spoke out about the difficulties of watching her longtime friend suffer from the disease's side effects. But she also noted how admirable and inspirational Bennett's efforts to continue performing were. 

"It's hard to watch somebody change," she said during an October interview with 60 Minutes. "I think what's been beautiful about this and what's been challenging is to see how it affects him in some ways but to see how it doesn't affect his talent. 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."

And their friendship always remained that magnificent. When Gaga was nominated at the 2023 Oscars for Best Original Song, her longtime collaborator made a rare statement celebrating her. 

"Congratulations to the amazingly talented @ladygaga on her 4th Oscar nomination!" he tweeted alongside a photo of the duo. "Today, Lady Gaga makes history as the first artist to receive three nominations in the ‘Best Original Song' category at the #Oscars. So proud of you!"