Well, I'm no expert, but Speech Pathologists tell me that singing is handled by a different part of the brain than speech. Whatever, just pay attention next time you are in a group setting at an assisted living facility or nursing home. You'll probably see a lot of smiling faces as you hear the residents singing songs from their youth.
For more information, check out the article, "The Power of Music" in the March 2013 issue of the AARP Bulletin. Another great source is Robbin Rio's book, "Connecting Through Music With People With Dementia (http://www.jkp.com/catalogue/book/9781843109051).
Then try a singalong with your loved one. You'll be glad you did.