Simple Feasts were, according to the Salisbury use, those on which only the initial words of the antiphon to the Benedictus and Magnificat were sung. They were comprised under three classes, the first, of nine lessons, with triple or double invitatory; the second, of three lessons, with double invitatory; the third, of three lessons, with simple invitatory; the latter, in distinction from the former two, were marked "sine regimine chori." Simple feasts, like ferials and vespers, had no first vespers.
In the Roman use simple feasts, without ruling the choir, are classed as simples; the simple, with ruling the choir, as semi-doubles. Accordingly, the highest class of Salisbury simples became the Roman doubles, to which succeed greater doubles, doubles of the second, and doubles of the first class.