My mother has vascular dementia. She is quite high functioning. Highlights are short term memory, time travelling, and most recently singing gibberish repeatedly, or actually singing comments that she then changes to rhyming words. This is usually in bed when she wakes up, or when driving in the car, or greeting people. Is this a common repetitive behaviour? It seems harmful enough, but could it be a medication issue? Generally we respond by making it a game and have good laughs together. So hopefully it is an okay behaviour.