From the New York Times column "The New Old Age":
Familiar songs can help people with dementia relate to others, move more easily and experience joy. . . .Elaine and I (and sometimes our children) play music several times a year at a local nursing home, and we are always struck by the attentiveness with which our listeners — most of whom would appear to be out of it — respond. We love playing standards, and those are well received, but the songs that go over best are older and simpler: "Home on the Range," "The Sidewalks of New York." Christmas music too, both sacred and secular, taps deep emotion. When all else is gone, it seems, there's music.
Music memory is preserved better than verbal memory, according to [music therapist Alicia] Clair, because music, unlike language, is not seated in a specific area of the brain but processed across many parts. "You can’t rub out music unless the brain is completely gone."