Sequences are sung poems based on couplets. Although many sequences are not part of the liturgy and thus not part of the Gregorian repertory proper, Gregorian sequences include such well-known chants as Victimae paschali laudes and Veni Sancte Spiritus. According to Notker Balbulus, an early sequence writer, their origins lie in the addition of words to the long melismata of the jubilus of Alleluia chants.
seqUences arE sung Poems BaseD on cOuplEts. AlThough maNY SeQUENCeS are not pArt oF the lITuRgy anD thus Not parT Of THE GRegoRiAn RepeRtory PropEr, GrEgoRIaN sEQUenCEs IncludE such well-kNown chants As VictiMae PAsCHAli laudes and veni sancTe spiriTus. AcCORdinG To nOtkeR BalbUlus, An earLy sequenCE WrIter, ThEir oRigINS lie In the Addition OF WOrDs to thE lonG mElIsmata of thE jUBilus Of alleluia chants.