His mind succumbing to Alzheimer's disease, country legend Glen Campbell can still summon strength through his voice and he has seized on it to bid farewell to the world.

A fixture on country music charts since the 1960s, the 81-year-old on Friday released what with near certainty will be his final album, aptly entitled "Adios."

With Campbell's memory fading, he turns to music to rekindle a life's worth of souvenirs on songs such as "Arkansas Farmboy," which recalls his hardscrabble youth as one of 12 children of a sharecropper in the southern state.

Yet Campbell, his voice clutching onto its sturdiness, is neither melodramatic nor melancholy on "Adios," instead throwing himself a bittersweet farewell party.

Campbell, who achieved crossover success on the US and British pop charts with hits such as "Rhinestone Cowboy" and "Wichita Lineman," recorded his latest album as a sort of last testament just as his Alzheimer's was becoming more severe.

He went into the studio in Nashville after in 2012 completing a difficult final tour, which was documented by the movie "Glen Campbell: I'll Be Me."

The film, which generated the Grammy-winning song "I'm Not Gonna Miss You," showed the star still instinctively fluent on the guitar yet struggling to remember lyrics and setlists and, by the time of his final show in Napa, California, barely able to lead his band.

Campbell's family released the final album as the singer enters the late stages of Alzheimer's, the disease most commonly experienced by seniors who lose their memory and gradually their bodily functions.

Kim Campbell, the singer's fourth wife who has become an advocate for Alzheimer's caregivers, in March told The Tennessean newspaper that the artist had lost most of his ability to speak and understand language.

- 'Adios' with lightness and joy -

Like many of Campbell's hits, the 12 songs on "Adios" -- primarily covers -- straddle the boundaries of country, incorporating the gentle arrangements of soft rock.

A cello brings a new romanticism to "Postcard From Paris" as Campbell, the twang in his voice forceful and bright, recalls the City of Lights in a song by his longtime collaborator Jimmy Webb that was most famously performed by John Denver.

Willie Nelson appears on "Adios" to duet with Campbell on "Funny How Time Slips By," which country music's premier outlaw had written early in his career for Patsy Cline.

Together Nelson and Campbell infuse the song with the feel of pop standards as they are jogged by lesser memories that they struggled to remember, like pillow talk with a former lover.

On the title track, also originally by Webb, Campbell again says goodbye not with sorrow but wistfulness as he recalls the sunset on the California coast.

Campbell, even aware of his own mortality, brings a light optimism to "Don't Think Twice, It's All Right," the oft-interpreted Bob Dylan tune whose original was a minimalist guitar confessional.

Rollicking with a folksy band instead, Campbell picks up the tempo as he updates Dylan's words: "I'm headed down that long, lonesome road, babe / Where I'm bound, I can't tell.

"But 'adios' is just too good a word now / So I'll just say, fare thee well."