What's the Name of That Book??? discussion

the book follows the perspective of a teenage boy who is part of a mismatched family of amazingly powerful monster hunters (at least, i think they're killing monsters, I don't fully remember). the parents are overworked and the mc doesn't seem to be able to really connect with them. all the family can kill people very easily, and it's much more difficult to not kill. each monster hunter has a mark on their arm for each day that they go without killing, and different people have different kinds of marks (one of the characters has stars). the only girl in the family has arms covered in marks, but then one day she has to kill and then they're all blank again. one of the monster hunters can kill by playing the violin (I think?). they spend quite a lot of time underground, I think. also i remember for some reason it contained the link "things that go bump in the night" (maybe in the blurb...?)

It sounds like This Savage Song by Victoria Schwab

Yes, you're right, thank you for making sense of a very garbled memory!