Sure, one can/must/should show mutual consideration in the neighborhood, but everything has its limits somewhere. The neighbor can't be held responsible for the hypersensitivity of the neighbor lady, and therefore I personally wouldn’t restrict myself in that regard. That may sound harsh, but that’s my personal opinion.
So if my neighbor came to me and described the situation as does here... I would definitely start to think. In the end, continuous music listening wouldn’t be that important to me. And no matter how you look at it, it is inconsiderate to constantly blast the neighbors with sound.
I assume isn’t insisting on complete silence, but is bothered by the really constant noise.
What would be tolerable then?
I would really consider selling only if there is absolutely no solution with the neighbor.
I think going there, clearly expressing with "I-messages" how one experiences it, up to the point that selling the dream house is on the table. The neighbor will have to respond somehow. So as I said, personally, that would really get to me as a neighbor. That one is not willing to meet the other halfway even a little bit, I find simply pathetic. Sorry, . Does it have to be 24/7 constant noise? Going down to 0/0 leaves plenty of room for a compromise.