Glen Campbell still does a mean Donald Duck impression. That's not the only skill he has left, but as shown in James Keach's heartbreaking documentary, many of his more important facilities have been leaving the pop music legend as he slowly succumbs to Alzheimer's. The movie follows Campbell and his family as he goes on tour to support his final album, a tour that they know will be his last, one that comes with no small amount of risk as the disease begins to rob him of his memories and his sense of self. While he has trouble finding the bathroom in his own home, playing music in front of an audience is one of the few places where he's still his old self, but even that's slipping away, and some shows go better than others as Campbell gets confused and frustrated. It's a remarkably unflinching portrait of a family dealing with their patriarch disintegrating, made all the more unsettling by footage of Campbell in his virile prime in the 1960s and 1970s. And even if hits like "Wichita Lineman" or "Rhinestone Cowboy" are not among your jams, it's impossible to not get swept up by the emotions on display, even when that includes pure, helpless horror.