Constant humming and singing with Alzheimer's is considered to be a method of communication. It is very common and seems to provide comfort to the individual. It often reflects emotion (for instance, anxiety) or an internal mood and serves as an alternative means for one who has lost the 'gift of gab'. Sometimes it can create a 'disturbance' in public places like a doctor's office, a movie, theater or a restaurant. If this is a regular behavior for your mom, you may need to plan your outings where she can hum or sing without losing her dignity. Always try to remember she is trying to say something and attempt to respond in kind.