126:2 The Sages also instituted that when arranging a festive meal for guests, even for the sake of a mitzvah, one should not provide every type of food that might be served at such a meal. (Meals on Shabbos and yom tov should not lack anything – Mishnah Brurah 560:5.) Similarly, a woman should not wear all her jewelry at once. Before his wedding ceremony, a groom puts ashes on his head at the place where tefillin go. The veil used to cover the bride may not have threads of silver or gold. Similarly, the practice at the time when an engagement contract (“tannoim”) is written is to break a dish after reading it as a reminder of the destruction. One should use a dish that is already broken for this. Under the wedding canopy (chuppah), the groom breaks a glass; this should be a whole glass. (This does not violate the prohibition against wanton destruction because it is being done to impart a moral lesson – MB 560:9.)
126:3 The Sages further instituted that one should not listen to any musical instruments, or even to singing. (Some say that this refers specifically to those who are accustomed to musical accompaniment, such as kings, or at a feast – Rema 560:3.) One should not sing at festive meals except for songs of praise that were written for that purpose, such as zemiros on Shabbos. Other songs, however, may not be sung.