Chant scholarship provides a fairly standard description of the Kyrie, in terms expressing very clearly what a typical example was like in the post-Carolingian era. There is no disagreement here, as there is with the sequence and trope, over how to treat the genre. Describing it seems to be a simple task. The chants are nine phrases long, with one phrase for each petition of the Ordinary text:
The relation among the phrases varies from complete identity of all nine to nearly the opposite extreme, yet in most cases the phrases are grouped by threes, giving the melody a tripartite shape like that of the text. Certain of the melodies were sometimes underlaid with syllabic texts expanding or replacing the Ordinary petitions (e.g.: Kyriefons bonitatis, Pater ingenite, a quo bona cuncta procedunt, eleison). Medieval commentaries on the liturgy (such as Amalar's Liber officialis) and exegesis of these texts make it clear that the Kyrie was thought of as being Trinitarian, with the first three petitions directed to the Father, the next three to the Son, and the last three to the Holy Spirit.