NASHVILLE (AP) — On television and on stage, Glen Campbell was a superstar with boyish good looks, a flashy smile and wit, but it was his last performance on screen that exposed a more vulnerable side that touched many of his fans.

Campbell, one of the most popular entertainers of the 1960s and 1970s and singer of such familiar songs as "Rhinestone Cowboy" and "Wichita Lineman," died on Tuesday at the age of 81, according to his family. He was diagnosed with Alzheimer's disease in 2011 and rather than retreating, went on a farewell tour that dealt with his illness and decline with the same candor he'd addressed his relationship troubles and addiction struggles earlier in his life.

His struggles to continue performing and recording after the diagnosis was the subject of an award-winning 2014 documentary called "Glen Campbell...I'll Be Me." The last original song he wrote and recorded for the film, "I'm Not Gonna Miss You," won a Grammy for best country song in 2015 and was nominated for an Oscar for best original song. The film's soundtrack also won a Grammy in 2016.

The documentary, which chronicled his 2011-2012 farewell tour, offered a poignant look at his decline from Alzheimer's while showcasing his virtuoso guitar chops that somehow continued to shine even as his memory unraveled. His family became his caregivers. His band backed him up on stage when he forgot chords and his fans would finish the song when he forgot the lyrics.

Those involved with the film said he remained happy and upbeat throughout the production, always telling jokes to get a laugh.

"He wanted to tell the story of his Alzheimer's disease," said director James Keach, who also directed the Johnny Cash biopic "Walk the Line." ''He was told to hang up the guitar and instead he proudly walked out and said, 'This is who I am. There's no shame in my game and I am going to go out singing the song.' That was Glen."

Caregivers and family members of those with the disease immediately connected to the film that showed him trying to navigate with confusion what once had been familiar places for him, such his home, the stage or the recording studio. The film also helped remove some of the stigma associated with the disease.

"Glen was a courageous advocate on behalf of Alzheimer's, not only bravely sharing his diagnosis with the world, but continuing to bring joy to his fans through his music while facing the disease so publicly," Harry Johns, president and CEO of the Alzheimer's Association wrote in a statement. "Glen and his family helped to bring Alzheimer's out of the shadows and into the spotlight with openness and honesty that has rallied people to take action on behalf of the cause."

"I had people come up after the film who had family members or themselves had Alzheimer's who said, 'I no longer feel ashamed,'" Keach said.

"I'm Not Gonna Miss You," which was recorded with members of Phil Spector's famous Wrecking Crew band, was based on a comment that Campbell mentioned to his co-writer and producer Julian Raymond when people would bring up his disease.

"He said, 'It's not like I am going to miss anybody anyway,'" Raymond said. "It's a strange title but he said it, and I know what he was trying to say."

The lyrics start off "I'm still here, but yet I'm gone/I don't play guitar or sing my songs." It was a farewell song to the people he loved, but with the message that he would be OK as the disease progressed.

Ashley Campbell, one of his daughters who played in her father's band and was one of his caregivers, said in an interview with The Associated Press in May that her father's honesty with the illness helped so many families.

"Just because my dad is a celebrity doesn't mean he doesn't have the same problems like other families are going through," Campbell said. "It was nice to know that we helped people not feel so alone."

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Follow Kristin M. Hall at www.twitter.com/kmhall