The Jewish community of Cologne, Germany, designated the 23rd of Nissan as a day of fasting and mourning to commemorate the Jews of Cologne massacred in 1147 during the Second Crusade. In remembrance of the tragic death of Rabbi Akiva's disciples who died in a plague in the weeks between Passover and Shavuot, several mourning practices are observed during this period: no marriages are conducted during this time, and like mourners, we don't cut our hair or enjoy the sound of music. Customs vary as to the proscribed activities and the dates during which the mourning is observed; consult your rabbi as to the traditions followed by your community.