Hi,
1. The best medicine for depression is to mingle with people. If you can enable that, then a lot of the problems go away.
2. It may be best to look around on her behalf and search for clubs, gatherings etc that elders go to, to share, laugh out etc.
3. Keeping the phone on the ear is terrible for me, i can only imagine how tough it is for your mom. Please get a jbl flip kind of bluetooth speaker which can automatically connect to your smartphone and she can hear loud and clear. The speaker also has a mic and she can speak to the speaker directly instead of speaking to the phone.
4. Talk a lot to her - do not judge (not saying you are doing it, just saying). Just hear her out and sympathize with her issues. Ex: Say "Yeah that aunt, i agree she should mend her ways" instead of saying "we cannot change people, so we should learn to live with them". Do not offer solutions, just hear her out.
5. Finally, please take her to a doctor. Depression can be reduced by taking medicines. There are mood elevators, anti-depressants which make one feel lively and energetic.
Sorry this post is in no way related to your query (music system). Just felt like adding my two cents because i have seen depression from very close quarters. It is very unsettling for the person going through it. Sorry for taking the liberty to give unsolicited advice.