As far as I know, the minhagim of when to observe the restrictions of sefira are not intended as the practice of aveilus. These minhagim are simply to make a remembrance of the talmidei Rabi Akiva whose deaths were the result of their failure at maintaining proper social relationships with each other – despite being talmidei chachomim. There is a powerful lesson in this. That is, without a single challenge, the most significant aspect of the restrictions of sefiras haomer. In order to make this mark, the chachomim enacted certain restrictions. One was the refraining from making weddings. The music thing is not one of their takanos. The Mishna Berura makes specific reference to ?????? ????????, which essentially refers to live music and dances. Recorded music is not part of that. It is common practice to refrain from recorded music, especially as the quality has improved to the point that one can conduct dancing with a DJ playing recorded music. Similarly, the slow music, like the nigunim of dveikus and hisorrerus would not be included. The presence of musical instruments is at the best, a secondary issue. Vocal presentations that are actually simcha-type nigunim that are realistic enough to make someone dance would likely be problematic in the spirit of the law.
I do wish there was more preoccupation with the matters of tikun hamidos that needs to characterize sefiras haomer, with the inherent preparation for Kabolas Hatorah. The issues with music are a far second to the preparation for Kabolas Hatorah.
An addition, if one follows the minhag of the Ram”o (s’iff 3) who describes the “second minhag” in which the time range for these restrictions goes from Rosh Chodesh Iyar, one may attend a chasunah that is made by someone who follows the “first minhag” that extends only until Lag baomer, and vice versa. It is about making the remembrance, not living in aveilus.