Just a few months apart a while back - at least within the same year - I had these two experiences when doing music in nursing/convalescent/rehabilitation centers:

1) I played and sang for a man who was in a coma and had shown absolutely no sign of response to anything for the previous 6 months or more, and after I played and sang softly for him at his bedside, he squeezed my hand. The nurses and aides were amazed and thrilled1

2) I played at the bedside of another, seemingly non-responsive, old woman, who gazed at me as I serenaded her, seeming to be touched and enthralled by my music.   
As I leaned towards her, upon finishing the song, she looked right into my eyes and said,""Get the hell out of here!"


It's best to avoid easy stereotypes and overgeneralizations about the elderly, the infirm, or the mentally challenged.