Halachic question relating to sefirah

If you are at a Sheva Brachos you can have music. It’s a Seudas Mitzvah and trumps the Minhag of Sefirah. Also, not all are Noheg to allow weddings before Rosh Chodesh Iyar.

If you hold of part 2 of Omer for mourning, thou mayest have music at the wedding; Notwithstanding, if your Sheva Berochos run into Iyyor, they are to be musicless, like someone marrying on say Tammuz 15th, whose Sheva Berochos after Tammuz 17th also have to be musicless.

As far as guests who observe 1st 33 days attending wedding of someone during last week of Nisson, at time of wedding thou art on turf of Baal[as] Simcho and hence follow his/her Minhog & are allowed to partake in music. That day still counts towards thy 33 days, as you couldn’t shave. But cannot listen to music in car on way to of from that wedding.

This being subservient to Minhog of Baal[as] Simcha only works for Availus of Omer or 3 weeks if invited to Yemenite wedding before Roch Chodesh Ov, but for mourner of a relative {i.e. Sheloshim & Yud Beis Chodesh}, this facet would not work.

DY: No offense to the Rav who Paskened it (and there are definitely opinions in the Achronim that say like him), but going up against Rav Moshe on a P’sak of his that has been near-universally accepted is usually foolish. (I can’t say anything more, obviously, because I don’t know who this Rav is; if it was someone anywhere near R’ Moshe’s caliber then I guess I’ll retract my previous statement.)

To 147. Look at Igros Moshe, Orach Chaim chelek bais siman 95 towards the end, paragraph beginning with “U’bdvar haekudin”. It seems to be clear that music and dancing with participation by all is permitted throughout Sheva Brachos even after Rosh chodesh for wedding before rosh chodesh and after Lag B’omer for weddings on Lag B’omer. I have not seen anyone who does this but Rav Moshe zatzal seems to imply that it is the norm in such instances.