ca and Joseph: This is so backwards it’s hilarious (and I say this with the utmost respect; it’s a mark on what Frum society is looking at, not either of you personally). The reason the Minhag developed not to listen to music is from the fact that music leads to dancing and dancing at Simchas is Assur during Sefirah. And yet the issue you guys are discussing about being at a wedding is because there’s music there!
To answer Joseph’s question, all of the major Poskim of the last generation allowed it. The most famous (and Lomdush) of the reasons is R’ Moshe’s T’shuvah, which is OC 1:167, I think. Maybe 157?