Several Introits in mode 3, including "Loquetur Dominus" above, exhibit melodic similarities. Typically, a handful of Introits rotated duty throughout the liturgical year. Stanford did not set introits but rather Latin texts of different origin. Introits, like Offertories and Communions, are believed to have evolved from simpler reciting tones. Introits cover the procession of the officiants. As revised in 1970, the Roman Missal also provides alternative Introits. In the musical idiom of Gregorian chant, Introits normally take the form antiphon-verse-antiphon-doxology-antiphon.