BS”D
Very quickly:
1) there is a difference between halacha and “past nisht” meaning inappropriate. The 4 inches is apparently halacha whereas some supposedly Jewish and most non-Jewish music may be viewed as inappropriate. Inappropriate depends on who you are and where it will lead you. For instance, shhhh…when I am up very late I will listen to the French Jewish singer or some old muzika mizrahit on YouTube to stay up. Inappropriate? Well, not really in some frum circles, particularly in France or Montreal where I picked up my Macias tayve LOL and miles above the level of my present community – but not something I would do in front of anyone else because the words are barely kosher.
2) If you start thinking of yourself as a ben/bas Melech then you will see that both that which is ossur and that which is inappropriate are not of interest to you because YOU will feel you have a purpose in life and are above doing things like that. If you want to be like the people around you and you don’t see yourself as special which is the point of all the mitzvos and minhagim anyway then u will see them as impositions and a pain in the neck.