A Jewish soprano (professional female singer) can sing inside a not Jewish cemetery (not during pray) for a concert?
If there are no men there then it isn’t problem at all, (although it isn’t particularly tasteful to make a concert inside a cemetery). However if there are men there, it is problematic, because there will most probably be some Jewish men there, and it is causing them to sin by them hearing a woman singing. Secondly, for the woman herself, chazal say “kol bisha erva” that a woman’s singing is considered erva, therefore she should not be singing in public in front of foreign men, the same way she should not be exposing herself improperly in public, even though the people seeing her are all goyim.
There is a famous story told about the mother of world renowned posek R’ Wosner. that when she was a girl, she wanted to sing in the opera because she had a beautiful voice. This disturbed her parents very much because it isn’t tznius for a Jewish girl to sign in front of foreign men. There was a Gadol there that told her parents that he will speak to her. He asked her, “Why do you want to sign in the opera?” She answered him that she had a good voice and she wanted to be famous”. The Gadol then told her, that he will make her a deal. If she is willing to give up being famous for the sake of tznius, he will give her a bracha that she will have a son whose word will be heard all over the world! She agreed and that is what happened. Because she was careful not to sign in public, she merited having a son whose halachic rulings were known all over the world.