In the Sephardic tradition, recital of Selichot in preparation for the High Holidays begins on the second day of the Jewish month of Elul. In the Ashkenazic tradition, it begins on the Saturday night before Rosh Hashanah. If, however, the first day of Rosh Hashanah falls on Monday or Tuesday, Selichot are said beginning the Saturday night prior to ensure that Selichot are recited at least four times. This may be because originally the pious would fast for ten days during the season of repentance, and four days before Rosh Hashanah were added to compensate for the four of the Ten days of Repentance on which fasting is forbidden - the two days of Rosh Hashanah, Shabbat Shuvah, and the day preceding Yom Kippur - and, while the fasts have since been abandoned, the Selichot that accompanied them have been retained. Alternatively, the Rosh Hashanah liturgy includes the Biblical phrase, "you shall observe a burnt offering", and like an offering which needs to be scrutinised for defects for four days, so too four days of self-searching are needed before the day of judgment.
Selichot refers to both the poetic piyyutim that compose the service as well as to the service itself. Sephardic Selichot services are identical each day. In the Ashkenazic tradition, different texts are recited on the different days. Though the text and length of specific prayers varies from day to day, the overall format remains the same. The service begins with the recitation of Ashrei (Psalm 145), followed by the Half-Kaddish.
Selichot are usually recited between midnight and dawn. Some recite it at night after the 'Arvit service or in the morning before the Shacharit service due to the convenience of synagogue attendance at these times.
Arguably the most important and certainly most popular night of Selichot in the Ashkenazi tradition is the first night, when many women and girls as well as men and boys attend the late-night service on Saturday night. The hazzan wears a kittel and sings elaborate melodies. In some congregations, it is not unusual for a choir to participate in this first night's service. This night also has more Selichot than any other night prior to Rosh Hashanah eve. The other nights are more sparsely attended and those services are often led by a layperson, rather than a trained musician, and with melodies that are less elaborate than the first night