ZD – I think that originally there was a takana that no one could listen to music anywhere (chasunas, etc may have been an exception), but the Poskim allow it since we are too emotionally weak nowadays and couldn’t survive without music. I believe Rav Moshe Feinstein has a teshuva about it.
There is a separate takana about live music in Yerushalayim even at a chasuna. As far as I know everyone holds by it, but there are different opinions regarding the details (what exactly counts as part of Yerushalayim? Can you have a one-man band? etc.)