I think the most interesting thing is people with full blown Alzheimer's being able to play their instruments. . . Just amazing stuff.
Yes, it is amazing. I think I saw the Tony Benett video. Clearly, music cannot prevent brain decline but the UK and other research seems to suggest that it can delay the decline. I understand that the cerebellum plays a big role in muscle memory which might explain Tony's skills despite his other limitations.
Donald Hebb (Hebb's Rule) back in the 1940s studied this.