Glen Campbell, 2012

Glen Campbell arrives at the 2012 CMT Music awards at the Bridgestone Arena on June 6, 2012 in Nashville, Tenn.

Rick Diamond/Getty Images for CMT

The last time the public saw Glen Campbell perform live on TV, he was the recipient of a Grammy Lifetime Achievement Award on Feb. 12, 2012.

Just eight months before, he had taken the rare step of announcing publicly that he was suffering from Alzheimer's disease, becoming the first musician of significance to make such a proclamation even as he continued one last, valiant tour. Alzheimer's -- or "part-timers," as he playfully dubbed it -- finally claimed him on Aug. 8, but even in that Grammy appearance, Campbell seemed a tad confused as he sang "Rhinestone Cowboy" one last time.

He was.

"I'm playing guitar, I go off and get him for his cue, and he looks at me," recalls producer Julian Raymond. "I go, 'Are you ready to go?' He says, 'Where are we going?' 'We're going out to sing.' 'What are we singing?' 'We're doing "Rhinestone Cowboy."' The main thing -- you've got to be calm with him all the time. But I'm thinking, 'Oh shit.' He goes, 'Do I need my guitar?' I go, 'No. You're just going to sing.' And this all happens within like five seconds, and Blake Shelton's out there going, 'And now, the great Glen Campbell…'"

The audience, at home and at the Staples Center, knew the significance as Campbell pulled off that last performance, and it was an appropriate curtain call for the singer and guitarist, given that his image for Americans was burnished on TV through The Glen Campbell Goodtime Hour. The weekly series ran on CBS from 1969-1972, fortuitously overlapping with the peak commercial years of his recording career and providing a forum for his multiple assets: fierce guitar skills, a smooth voice, boyish good looks and a comedic personality.

Raymond, who has produced such disparate acts as Justin Moore and 1990s pop-rock band Fastball, came onboard with Campbell late in the game, producing the 2008 album Meet Glen Campbell and 2011's Ghost on the Canvas. Then employed at Capitol, Raymond experienced Campbell's best in an enviable way, digging up the original recordings and hearing the isolated tracks of that classic late-'60s material, including "Gentle on My Mind," "Galveston" and "Wichita Lineman."

"Every single one of those songs is Glen is playing and singing at the same time," says Raymond. "He's not overdubbing. He's on the tracking session, singing and playing acoustic guitar, and they're bleeding into each other. So even if you went to remix that stuff, it'd be very difficult to get anything different than what you got, because the guitar was blended just right to not get in the way."

But Raymond also experienced the fading version of Campbell. The Alzheimer's diagnosis came in 2011, but even in their first collaboration, there were signs that something was wrong.

"He kept asking the same questions over and over again -- 'Where's the bathroom again?' " says Raymond. "So I'd show him where it was. It was happening over and over again. He told the same jokes and the same stories over and over again, but I just thought, 'Okay, the guy's 75 or whatever. He was just like my grandfather, he's getting forgetful, it comes with old age.' And I didn't go there -- Alzheimer's, dementia -- I didn't know anything about that, so I just figured it's the way he is and who he is, because for the most part, he nailed those songs."

Ghost on the Canvas, in particular, accomplished many of the same creative goals that Johnny Cash achieved in his latter-year albums with producer Rick Rubin. The songs -- many of them originals, co-written by Raymond and Campbell -- address aging and spirituality with an admirable frankness. But where Cash's American Recordings projects were stripped down and weighty, Ghost had all of the rich uplift that accompanied that classic Campbell period of the late 1960s.

"I wasn't trying to do what Rubin did with Cash," says Raymond. "What he did was really cool. It was a really cool interpretation. It was darker. It was unique. 'Hurt,' in my opinion, is one of the greatest recordings ever made by anyone. But with Glen, I just always felt his stuff was spirited and upbeat, and I was just so enamored with [producer] Al de Lory and [songwriter] Jimmy Webb and all those people that were part of those records. I kind of wanted to do something that was like that and keep it in the tradition of what Glen was back in the day."

It was Raymond who connected producer-director James Keach and Campbell's wife, Kim Campbell, leading to the documentary Glen Campbell: I'll Be Me. Raymond accompanied Campbell on parts of the Glen Campbell Goodbye Tour (its very name echoes The Glen Campbell Goodtime Hour), and they co-wrote "I'm Not Gonna Miss You," which received an Oscar nomination for best original song and won a Grammy for best country song.

By the time they won the Grammy, Campbell's memory and perception had deteriorated significantly -- he kept trying to drink out of the gramophone-shaped trophy -- but it put a coda on the movie's significance.

"I got so many letters and emails from people saying how much 'I'm Not Gonna Miss You' changed their life and the movie changed their life, and when you can create art like that that moves people, it's pretty darn special," says Raymond.

That's what makes the final years of Campbell's life so significant. He was uniquely gifted with both talent and commercialism -- during one period in the late 1960s, Capitol reported he was outselling his labelmates The -Beatles -- but his final years helped raise awareness of a debilitating disease. Shortly after he stopped touring, he no longer recognized a simple guitar, even though that instrument was such a significant part of his being. Prior to losing his mobility, he was prone to wander in the odd hours of the night, and he soon failed to identify even his family members.

Campbell's descent shone a light on a horrific condition. It was particularly stunning because his body of work -- including "By the Time I Get to Phoenix," "Rhinestone Cowboy" and Ghost on a Canvas -- was such a symbol of artistic strength.

"The last time I saw him, he just didn't have the mannerisms of Glen Campbell," says Raymond. "The twinkle in his eye, the way he'd move or speak to you -- all of that was gone. The character and the spirit and the soul of the man wasn't there anymore. It was like somebody that you didn't really know. So I'm happy that he's at peace. He's where he always wanted to be. He talked about it all the time. He was excited to meet his maker and get up there and do his thing."