LO was diagnosed with multi infarction dementia few years ago. She is 88. Recently has asked us whether we can hear the music she is hearing? She also has started singing and dancing - seemingly from internal stimuli? And she has episodes in last few weeks where she awakes and complains of being cold and having body aches all over. We get her to sit down, she will dose on and off and then once awake again he has no recollection of how she got to where she is sitting and why.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5353248/
MES is associated with hearing loss. Dementia can also bring on all sorts of hallucination type events, if this is not associated with hearing loss.
As dementia progresses, they will literally forget what happened 2 minutes ago; I see it my own mother who's 93 with moderate dementia.
Contact your mom's doctor to apprise him of the new symptoms and to see if he has light to shed or medication to prescribe.
Best of luck!