I have written an app for playing Music for dementia users.
It is now on Google Play, for Android mobiles called Dementia Player.
Dementia Player.1 is for older android mobiles and tablets. https://play.google.com/store/apps/details?id=com.thunkable.android.adams1stephen.DemPlayer1
Dementia Player.2 is for the ones with Kitkat (4.4) operating system or later. https://play.google.com/store/apps/details?id=com.thunkable.android.adams1stephen.DementiaPlayer2
Explanation is on the web site.
Once set up, dementia users can press a flashing coloured square and get one of 9 songs, of their choice.
It is free to use, asking people if they like it to donate to the Alzheimer’s Society UK.