One may sing happy songs at a se’udat mitzva, like the meal at a brit mila, pidyon ha-ben, or sheva berakhot. One may also celebrate a bar mitzva or bat mitzva during this period, but only on the actual day that the child comes of age.

The poskim disagree about a locale where people always have musicians at a se’udat mitzva: May one have them during the Three Weeks as well? Some say that one may do so, since the music is for the sake of a mitzva. Others, however, forbid this. One who wants to be lenient has an opinion to rely on, as long as this is the general practice throughout the year.

Therefore, in a locale where people always hire musicians for bar mitzva celebrations, one may do so during the Three Weeks. However, if some people hire two musicians and others hire three, it is proper to hire only two during the Three Weeks. The same is true of all mitzva celebrations: We follow the general practice of the rest of the year.

Once the month of Av arrives, one should not hire musicians for any celebration. Similarly, one should not play recordings of happy songs, and one may only sing along with songs that relate to the mitzva celebration. One may even dance a little in a circle, as many people customarily do at a brit mila celebration.[2]

Members of communities whose custom is to allow holding weddings until the end of Tamuz may hire a regular band for their weddings, because there is no celebration with a bride and groom without musical instruments. Even those whose custom is to refrain from getting married during these days may attend and dance at these weddings, as the joy they experience stems from a mitzva.