Well I did wonder that too, so maybe I didn't give the answer that George was looking for. The groups we go to don't usually volunteer to sing, but are happy to sing along with what we start off
However, I do remember one elderly gentleman with Alzheimer's doing a word-perfect and very beautiful rendition of "Kathleen Mavourneen". It is quite something to see that spark of distant memories re-ignite in people whose short-term memories are sadly deteriorating.