“I’m not a country singer,” Glen Campbell often said. “I’m a country boy who sings.”

Campbell, who died at 81 on Tuesday after a long battle with Alzheimer’s disease, became one of pop music’s biggest crossover stars with ’60s and ’70s singles like “Gentle on My Mind,” “By the Time I Get to Phoenix,” “Wichita Lineman,” “Galveston,” “Southern Nights” and “Rhinestone Cowboy.”

Whether performing songs penned by ‘60s chart titan Jimmy Webb or indie-rocker Paul Westerberg, Campbell played and sang with an effortless plaintiveness that made him a model for younger generations of artists like Keith Urban, Vince Gill and Brad Paisley, who, like him, felt comfortable moving between the genres of country and pop music. He had a boyish handsomeness that made his transition from the recording studio into world of television and film seem like a foregone conclusion. The records he made with Webb as writer and Al DeLory as producer practically defined country-pop crossover during the late ‘60s, and “Rhinestone Cowboy” and “Southern Nights” did the same in the ‘70s. Campbell’s recording spanned six decades, leading to his induction into the Country Music Hall of Fame in 2005.

As he battled publicly with Alzheimer’s during the final decade of his life, Campbell and producer Julian Raymond used his art to tell the story of his struggles with the disease. Those efforts — culminating with the 2014 documentary “Glen Campbell: I’ll Be Me” and the album “Adios,” released earlier this year — traced the arc of the disease as it stole first his memory and, only later, his talent, allowing Campbell a poignant curtain call.

Born near Delight, Arkansas — a town with a population of just 290 — in 1936, Campbell was a fabled seventh son of a seventh son, and one of 12 children. As a child, he made a makeshift instrument by stringing wire across an empty kerosene can, soon graduating to a three-quarter-size Sears & Roebuck guitar. By age 7, he was performing with his brothers on local radio shows.

As a teenager, Campbell left Arkansas for Texas and New Mexico, playing in bands and marrying twice before landing in Los Angeles. There, he briefly joined the Champs, who’d had a 1958 chart-topper with the iconic instrumental “Tequila.” He also began getting session work, even though he played only by ear. When asked if he could read music, he would say, “Not enough to hurt my picking.”

As a member of Los Angeles’ legendary Wrecking Crew collective of session musicians, he played on hundreds if not thousands of songs, including Elvis Presley’s “Viva Las Vegas,” the Righteous Brothers’ “You’ve Lost That Lovin’ Feelin’,” the Monkees’ “I’m a Believer” and one of his favorites, Frank Sinatra’s “Strangers in the Night.” Campbell also was a touring member of the Beach Boys, replacing Brian Wilson for a few months during 1964 and 1965. He played on many of the group’s hit records as well, including “Be True to Your School,” “Fun, Fun, Fun,” “Good Vibrations” and the “Pet Sounds” album.

Campbell released his first album in 1962 and his early singles occasionally appeared on the lower rungs of Billboard’s pop and country charts. His breakthrough came in 1967 with a pair of songs: John Hartford’s “Gentle on My Mind” and Jimmy Webb’s “By the Time I Get to Phoenix.” Those two singles would win Campbell four Grammys in 1968 — two in country categories, two in pop — and vault his career to a new level.

“By the Time I Get to Phoenix” established a creative template that would serve Campbell well: his voice, Webb’s material, and De Lory’s distinctively lush arrangements that skirted the line between pop and country. That team would be responsible for Campbell’s best-known hits from that era, including “Wichita Lineman,” “Galveston,” “Where’s the Playground, Susie” and “Honey Come Back.”

It was only a matter of time before Campbell’s good looks and outgoing personality inspired TV executives to put him in front of a camera. He had played in the house band for ABC’s musical-variety series “Shindig!” as well in the acclaimed multi-artist 1964 concert film “The T.A.M.I. Show” (which introduced both the Rolling Stones and James Brown to thousands of young Americans). In 1968, he hosted a summer-replacement show in the time slot for CBS’ “Smothers Brothers Comedy Hour” and was rewarded the following year with “The Glen Campbell Goodtime Hour.” Campbell’s musical tastes were broad enough to appeal to both young audiences and older viewers, and his variety show aired until 1972. In 1969, Campbell also co-starred with John Wayne in the Western “True Grit” (remade by the Coen Brothers in 2010), playing a young Texas Ranger who assists Wayne’s one-eyed sheriff, Rooster Cogburn, track a murderer.

The hit records didn’t come as big or as frequently for Campbell during the early ’70s, though he remained a familiar presence on television. He occasionally hosted “The Midnight Special,” a late-night music series, and in what must have been a challenging role, co-hosted the Country Music Association Awards in 1975, the year Charlie Rich famously burned the envelope revealing folk-pop sensation John Denver as the organization’s entertainer of the year.

In 1975, seeking to jump-start Campbell’s career, Capitol Records paired him with producers Dennis Lambert and Brian Potter. With records like the Four Tops’ “Ain’t No Woman (Like the One I’ve Got)” and the Righteous Brothers’ “Rock and Roll Heaven,” the Lambert-Potter team had built a reputation for helping established artists find second acts in their careers.

Their magic worked for Campbell, too. He’d found a tune by singer-songwriter Larry Weiss that perfectly described his career, the dreams he had and the compromises he’d made. When he insisted to Lambert and Capitol Records vice president Al Coury that he be allowed to cut it, Campbell discovered they’d each already heard the song and thought it would make an ideal comeback record.

“Rhinestone Cowboy” became Campbell’s first No. 1 on the Billboard Hot 100 and the defining song of his career. The session work may have built his reputation among fellow musicians, the TV show and ‘60s hits may have made him a star — but “Rhinestone Cowboy” cemented a lasting pop-culture legacy for Campbell.

Just as his career was ascending to new heights, however, his personal life was crumbling around him. According to Campbell’s 1994 autobiography, also called “Rhinestone Cowboy,” his second wife, Billie Jean Nunley, had introduced him to cocaine in the mid-1970s. The couple soon separated, an argument about the song “Rhinestone Cowboy” being the final straw.

“He said she hated that song,” says Julian Raymond, who produced Campbell’s final albums. “She just detested the song and thought it was a joke. She said, in so many words, ‘If you put that song out, you’re through.'”

Nunley filed for divorce just a few weeks after the single hit the top of the charts, and Campbell’s life began to spiral out of control.

“He was in pretty bad shape, psychologically,” says Lambert. “He put on a happy face for me and Brian, and he was the consummate artists. He took what he was doing very seriously. But he was in bad shape. You could tell he was hurting emotionally.” Campbell soon married Sara Davis, the ex-wife of singer-songwriter Mac Davis. That marriage last only three years, but, before it ended, Campbell got involved with country singer Tanya Tucker, 22 years his junior. Their tempestuous, cocaine-fueled relationship made for tabloid gold.

Campbell married his fourth wife, Kim Woolen, in 1982 and began to turn his life around. He got sober and returned to religion, recording several gospel albums and having the occasional country hit during the late ’80s and ’90s.

In 2003, Campbell fell off the wagon with a high-profile DUI in Phoenix, for which he served 10 days in jail. As part of his sentence, he also entered rehab at the Betty Ford Center, at which time doctors noticed some cognitive impairment. The impairment would progress to an official diagnosis of Alzheimer’s disease, which Campbell revealed publicly in 2011.

By this time, Campbell had already begun releasing an impressive trio of latter-day albums. “Meet Glen Campbell,” released in 2008, re-introduced the singer with covers of songs by the likes of Green Day, Foo Fighters and the Replacements, re-arranged by Julian Raymond to recapture the style of his early hits. The songs on 2011’s “Ghost on the Canvas” mixed more covers with original songs, written by Campbell and Raymond, that poignantly addressed the ongoing loss of memory and identity.  At the same time, he also re-recorded several of his early hits, releasing them in 2013 as “See You There.”

Campbell often joked about his disease, saying in 2013, “Some things I don’t want to remember. That’s how I look at it now.”

A 2012 farewell tour, for which Campbell fronted a band that featured three of his eight children, found the singer in fine voice. He sometimes forgot things — like which song he had just performed — but when he played his guitar, muscle memory took over as his hands moved across the strings.

Campbell entered an Alzheimer’s treatment facility in Nashville in April 2014, just days before the premiere of a documentary called “Glen Campbell: I’ll Be Me,” which chronicled the singer’s final tour and the progressing symptoms of his Alzheimer’s.

“I’m Not Gonna Miss You,” a song Raymond crafted from conversations with Campbell, received an Academy Award nomination in 2015 for Best Original Song, and is not only a deeply touching message from him, but a perspective inside the disease that has afflicted the final years of so many people.

I’m still here, but yet I’m gone
I don’t play guitar or sing my songs
They never defined who I am
The man that loves you ’til the end

You’re the last person I will love
You’re the last face I will recall
And best of all, I’m not gonna miss you
Not gonna miss you

I’m never gonna hold you like I did
Or say ‘I love you’ to the kids
You’re never gonna see it in my eyes
It’s not gonna hurt me when you cry

I’m never gonna know what you go through
All the things I say or do
All the hurt and all the pain
One thing selfishly remains
I’m not gonna miss you