It's important for you to be comfortable with your phone. It can be troubling when it's hard to hear the person you're speaking with. I am glad you reached out for help.
Here is a link from Apple on ways to overcome difficulties with hearing the caller on the other end: https://support.apple.com/en-us/HT203800
Can you tell us more about the music? Are these songs you uploaded to iTunes or streaming from the Apple music app?
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