deus israel and roman introits
John Boe
the roman wedding introit deus israel (its text extracted from book of tobit) was assembled during latter half ninth century using two initial and three cadential formulas that pervade urban repertory deuterus introits. at least fifteen additional can be identified within this modal group, by far most numerous among introits rome. one figure stands out rest these formulas, introducing a ‘paschal tone’ incorporating alleluias regularly interjected into eastertide narrow in range archaic style, paschal tone quotes office antiphon for easter week dating seventh or earlier, whose pitches – emblematic permeating eventually generated psalm-tone differentia formula used to begin many later introits, including .
Plainsong & Medieval Music