Hi Phil, what hearing aids is your mother wearing? Some are better than others at processing music. As a general rule you tend to find the newer and more sophisticated the hearing aids are, the better they will be at dealing with music more effectively. Hearing aids are designed primarily to enhance speech and some of the processes occuring in the background to this end can leave music sounding less than desirable.
If a hearing aid can detect the primary sound source is music with no speech present you would hope the hearing aids would automatically adjust their settings for a response more appropriate for music, the more basic hearing aids might need to be manually switched to a 'music' program to achieve this.
Another thought, some of the more recent hearing aids of the last year or two use frequency shifting to try to help with speech audibility, basically moving higher frequecies towards the middle frequencies electronically, it sounds quite different but can help speech but make music sound mighty peculiar!
If you post the hearing aids worn it migth be easier to see a way forward...
