Jubilus

in liturgical singing, an exalted, ornamented improvisation. In Gregorian chant, jubili were sung by soloists on the last syllable of the word “alleluia.” They were borrowed by the Christian church from Hebrew liturgical music. In order to facilitate memorization, the monk Notker Balbulus (A.D. 830–912) of the Abbey of St. Gallen arranged jubili in such a way that each syllable of the text corresponded to a note. This was the origin of the liturgical sequence.