On the eves of [[First Class Feasts]], [[Second Class Feasts]], and certain [[Third Class Feasts]], a special aggregate, known as the [[All-Night Vigil]]or Nocturne, may be served. In such case, the other aggregations may be altered slightly (e.g., including Little Vespers in the Evening Aggregate). Although there is some variance in practice, the All-Night Vigil generally includes at least Great Vespers, Orthros, and First Hour.