Alzheimers really is a monster..it robs you of your history, your loved ones, and eventually your life. By the time my father died of this he was unrecognizable as someone we knew...and I was relieved when he passed because the man I had known and loved had died years before.
While he still was able to recognize me he seemed to enjoy hearing me sing to him...."Daisy, daisy, give me your answer true..." or "Don't sit under the Apple Tree with anyone Else but Me"...he would nod and smile..music seems to touch some pts in a special way.
Have you read "Still Alice"? It is a powerful book.