It is customary during the first thirty-three days of the Omer period to observe certain mourning practices in commemoration of the tragic death of Rabbi Akiva’s 24,000 students that occurred during these weeks. The Shulhan Aruch writes that during this period one should refrain from haircutting and weddings should not be held.
The Magen Abraham (Rabbi Abraham Gombiner, Poland, 1637-1683), in his commentary to the Shulhan Aruch, adds that one should also refrain from listening to music during the Omer period. Although the Shulhan Aruch makes no mention of this practice, Jews have accepted this custom and one should therefore not listen to music during the first thirty-three days of the Omer. This is the ruling of Hacham Ovadia Yosef. It should be noted that this applies to both live and recorded music. One should not listen to music on the radio or on a cassette or disc player during the Omer. Especially during these weeks, it is appropriate to listen to recordings of Torah lectures and the like, rather than listening to music.
It is permissible to listen to singing that is not accompanied by music, such as a Hazan singing Pizmonim (hymns) or a cappella choirs and the like. The prohibition relates only to instrumental music, and one may therefore listen to vocalists singing without instrumental accompaniment.
May music be played at a "Se’udat Misva" (meal involving a Misva), such as the celebration of a Bar Misva, Berit Mila or Pidyon Haben?
Hacham Ovadia Yosef, in his work Yehave Da’at (vol. 6, 34), rules that music – both live and recorded – is permissible at such gatherings, since these events are held in the context of a Misva. This would also apply to a Siyum Masechet – if a person or group of people happens to complete a section of the Talmud during the Omer, such as if a Daf Yomi study group completes a Masechet (tractate) in this period. (We refer to a case where this happens to occur during the Omer, and not that they specifically scheduled their learning to finish in this period.) One may conduct a Siyum celebration with live music in all these cases. This is also the ruling of Hacham Ben Sion Abba Shaul (Israel, 1923-1998), in his work Or Le’sion (vol. 3). Hacham Ben Sion notes that since the Shulhan Aruch makes no mention of a prohibition against listening to music, and this is observed only as a custom, we may certainly be lenient in situations of a "Se’udat Misva."
As mentioned, the practice among Sepharadim is to observe these practices until the thirty-fourth day of the Omer. There is room to allow music on Lag Ba’omer for the celebration of the "Hilula" of Rabbi Shimon Bar Yohai; otherwise, one should not listen to music until the next day, the thirty-fourth day of the Omer.
Summary: One should not listen to live or recorded instrumental music during the first thirty-three days of the Omer, except during a "Se’udat Misva," such as the celebration of a Bar Misva, Berit Mila, Pidyon Ha’ben or Siyum. Likewise, music may be played as part of the "Hilula" celebrations on Lag Ba’omer.