Ailing country star Glen Campbell is still managing to surprise his family by revisiting old tunes on his guitar every now and again, despite battling severe dementia.

The Rhinestone Cowboy hitmaker, 78, was diagnosed with Alzheimer's disease in 2011 and the degenerative condition forced him to retire from showbusiness after a farewell tour a year later (12).

His wife, Kim Woolen, checked him into a full-time care facility in Nashville, Tennessee earlier this year (14) when his memory lapses and confused state made him a danger to himself around the home, but she admits the singer hasn't been robbed of all his musical skills.

She tells U.S. breakfast show Today, "(His guitar memory) comes and goes. Some days he'll give us a big surprise; he'll pick it up (and play) and we'll be like, 'Woah, where did that come from?'."

However, Campbell's disease has cost him the ability to hold a coherent conversation and his condition is so advanced, he is now in late stage six. Stage seven is considered the beginning of the end.

But Woolen insists her husband can still convey his feelings clearly.

She adds, "He's still Glen Campbell and he still loves and feels and expresses joy and sadness."