Indeed there is strictly no penitential Rite in the older Form, no "calling to mind our sins". It happens before Mass, the priest and servers, (and the people if they wish to) take part in an act of penance before going up to the altar, before the Mass starts, before the Introit. Thus the Kyrie is not about penance but about praise; us encountering the Eternal King who is the Creator of the World and us almost falling back again and again crying “have mercy”. But even Eleyson is not exactly the same as miserere and breast beating either, it is about the pouring of healing oil. Eleyson is of the same root as elaion, which means “olive tree and the oil from it”. It is about, gasping at God's glory which is too much for us.
Here is an example, it is the troped version of the Orbis Factor:
1. Orbis factor rex aeterne, eleison. Kyrie Eleison
2. Pietatis fons immense, eleison. Kyrie Eleison
3. Noxas omnes nostras pelle, eleison. Kyrie Eleison
4. Christe qui lux es mundi dator vitae, eleison. Christe Eleison
5. Arte laesos daemonis intuere, eleison. Christe Eleison
6. Conservans te credentes confirmansque, eleison. Christe Eleison
7. Patrem tuum teque flamen utrorumque, eleison. Kyrie Eleison
8. Deum scimus unum atque trinum esse, eleison. Kyrie Eleison
9. Clemens nobis adsis paraclite ut vivamus in te, eleison. Kyrie Eleison
It is about God's glory, not us and a preoccupation with our sin, though, the wretched priest continually remembers his sin but in a pious mutter in his heart. Yes, he proclaims his, non sum dignus, again and again but this is because he is encountering God's Glory
The Kyrie flows naturally into the Gloria, which is of course a highly troped version of the Angelic song at Christ’s birth.
Is it legitimate to use the troped Kyries in the Novus Ordo, anyone know?