Shloishes yemei hagbalah
There is a difference of opinion when the laws of Aveilus, the laws of mourning associated with Sefirah, the days of the Omer, cease to apply. Some people practice ShloishesYemeiHagboloh, the three days before Shavuos, as a time when the laws of Aveilus no longer apply, starting from the morning of Gimmel Sivan, while other people carry the laws of the Omer straight until Erev Shavuos and they only take haircuts on ErevShavuos. That is the opinion of Kabalah, and it is the Chabad custom as well. Even those who suggest that there is no mourning during the ShloishesYemeiHagboloh, nonetheless there is a discussion in Poiskim whether one is allowed to listen to music, RikudimU'mecholosShelReshus, music which is not associated with a Mitzvah. Chasunahs are permissible, but regular music not associated with a Mitzvah should not be listened to until ErevShavuos.
https://halacha2go.com?number=25