Q. Is it proper to make or attend a wedding or a sheva brochos with music on the night after Asara Beteves?

A. See prior question. Poskim mention that it would seem that there is no reason to avoid weddings on the night after the end of the Ta’anis, however some consider that since the activities and preparations for the night will certainly begin already on the day, this should be averted when possible. (Shulchan Hoezer 6, P’ri Hasade 1: 2, Yoshiv Yitzchok p. 80). See also Shulchan Aruch (E.H. 64: 3), and Aruch Hashulchan (ibid. 11) in regards to weddings on Motzei Shabbos. However, Chesed Yehoshua (2: 5) writes that many communities in Europe would avoid vehemently Motzei Shabbos weddings because of the inherent chilul Shabbos involved.
See also Nitey Gavriel (Bein Hametzarim 5: 23- 8: 7) in regards to avoiding fateful activities on a Ta’anis since it is a day of detrimental mazal.
Horav Shlomo Miller’s Shlit’a opinion is that in principle you can certainly celebrate a wedding or Sheva Brochos with music after the end of Asara Beteves, but when possible, on the onset it should be avoided.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a