Recorded music can be very effective as part of a recreational or music therapy program for dementia patients, especially if it's actually incorporated into a session led by someone who helps involve people in singing along, dancing, using rhythm instruments and/or talking about the songs and their history.

But this sort of thing does not require the facilitator to be a musician or entertainer at all. I thought this thread was more about suggestions for a singer/poet/storyteller who's involved in working with dementia patients for "Storytelling Week."   Northerner could do a program using recorded music as part of storytelling, but I gather the aim was to use his (her?) own musical skills as part of the program too.

As for singing live being "utterly bogus" and "reductive," that perspective misses the point of live singing, especially group singing. A live singer tends to involve the group more actively than recorded music, plus the act of singing per se has many healthful benefits and singing together with other people has even more.