@nhbfan I sympathise with both you and your mum! I suddenly started experiencing MES every night when lying down in bed before going to sleep while I was undergoing chemo and immunotherapy. It just started. Lawdy lawdy lawdy indeed!! The music started off being big band (not something I listen to!) Not unpleasant but weird. I looked it up and was able to just lean into it knowing I wasn’t going crazy. The type of music would also change - sometimes country and sometimes discordant interpretative slow tunes (again not genres I listen to). Suddenly one day I realised it had gone but couldn’t pin point when. It hasn’t come back and I’m no longer on those medications.

I take it your mother isn’t able to comprehend the condition. Can you perhaps speak with her doctor to see if there’s a possibility one of the medications she’s on might be causing it and something else might be used instead?
https://tinnitus.org.uk/understanding-tinnitus/what-is-tinnitus/types-of-tinnitus/musical-hallucination-musical-tinnitus/