Q. Is it proper to make or attend a wedding or a sheva brachoth with music on the night prior to the fast of Asara Beteveth?

Remoh (O.H. 550: 3) advises that if there is a Chupa on Asara Beteves on Erev Shabbos, Mincha and Vaichal are recited before the Chupa. However, Shulchan Aruch (551: 2) rules that no weddings are to be done during the Nine Days and Biur Halacha (ibid.) quotes from Eliahu Rabbo and Peri Megodim that it is possible that this also applies to Shiva Asar Betamuz and Asara Beteves.
Bais Avi (3,2,6) writes that the minhag is not to make weddings on the night of the Tenth of Teves since in reality the Ta’anis has already began but the prohibition to eat is only from the morning. Other Poskim are more lenient (Even Pina O.H. 45, P’ri Hasade 1: 2, Yabia Omer 6: 7, Tzitz Eliezer 7: 49).
Da’as Torah of the Maharsham (551: 2) advises that although the Chupa is permitted but one should abstain from dancing even on Asara Beteves. See also Halichos Shlomo (13: 1)
Horav Shlomo Miller’s Shlit’a opinion is that in principle and by the letter of the Halacha, it is permitted to have a wedding or Sheva Brachos with music on the prior night of the Ta’anis, however, when possible one should be stringent. (He pointed out to the Sdei Chemed – Ma’areches Choson Vekalo p. 21-22)

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