Glen Campbell's battle with Alzheimer's has progressed to the point where he is unlikely to ever perform in public again.

"He can't even tune a guitar now," Campbell's wife, Kim Woolen, told People magazine at the Open Hearts Foundation's 4th Annual Gala in Malibu on Saturday (May 10). "If I tune one and hand it to him he can still play, [but] not like he used to."

She adds that he can still "play a couple licks here and there, and he finds joy in that."

Campbell is now living in a full-time care facility near the family's home in Nashville, where he fills much of his time with daily visits from Woolen. Though she says his disease has been "absolutely heartbreaking" for her and the couple's three children, they try to stay positive.

"There's a lot of sadness," she admits, "[but] we just continue to try to make the best of every day and keep a sense of humor."

A film documenting Campbell's farewell tour, 'Glen Campbell ... I'll Be Me,' won the Gibson Music City / Music City Films Grand Jury Prize when it premiered at the Nashville Film Festival in April.