NASHVILLE, Tenn. (AP) _ Glen Campbell, the grinning, high-pitched country star behind such hits as “Rhinestone Cowboy,” “Galveston” and “Southern Nights,” has died. He was 81.

Campbell’s publicist Sandy Brokaw says the singer died Tuesday morning in Nashville.

No cause was immediately given, though Campbell announced in June 2011 that he had been diagnosed with Alzheimer’s disease and that it was in its early stages at that time.

His Alzheimer’s battle was chronicled in the Oscar-nominated documentary “I’ll Be Me” (2014).

Campbell was one of the biggest stars of the late 1960s and 1970s, selling more than 45 million records, including 12 gold albums and 75 chart hits.

He co-starred with John Wayne in the 1969 movie “True Grit” and had a weekly audience of some 50 million people for the “Glen Campbell Goodtime Hour” on CBS from 1969 to 1972.