Any Barbershoppper who's ever sung at a nursing home or senior center can attest to this truth, as reported by AARP:
Music therapists who work with Alzheimer's patients describe seeing people "wake up" when the sounds of loved and familiar music fills their heads. Often, after months or even years of not speaking at all, they begin to talk again, become more social and seem more engaged by their surroundings. Some begin to remember names long forgotten. Some even do what Alzheimer's patients often cannot do as their disease worsens: They remember who they are.
Neurologist Oliver Sacks wrote in his book Musicophilia that for Alzheimer's patients, music can be very much like medicine. "Music is no luxury to them, but a necessity, and it can have a power beyond anything else to restore them to themselves, and to others, at least for a while."