Here are two pictures of the beginnings of this Kyrie Fons Bonitatis in both latin and english, they have many more words to them which I have cut off to make a small image size for sharing.
**When the Kyrie is sung as a part of the Act of Penitence, a trope may precede each acclamation. **
all I can tell you is that the Kyrie Fons Bonitatis is found in the book “Cantus Selecti” published by Solesmes in the 1930s or 40’s. This is an example of the same Kyries Fons Bonitatis melody found in the Gradual Romanum , except that within the Romanum, the trope has been removed from the Kyrie.
ALL Kyries in the Graduale Romanum the official book of Gregorian Chant for the Church have tropes that were originally part of them, which have due to the protestant reformation, been removed from their Kyries. A great mistake I feel. This was the result of the Council of Trent in the 1550s…the Vatican II of it’s day. (though not as radical)
Troped kyries are an important part of Church history, all of latin christianity grew up hearing them between the 9th and 16th centuries on nearly all Sundays and Feasts. (As they also heard Sequences/Proses, which were removed from the Graduales for similar reasons, partly that they reflected the local dioceses and nations.)
There was of course an art to it, the tropes were very rich in theology and done in a specific way each time, the creativity was limited to a certain context and specification.
What was posted above is a product of the post-1970 era and is not created or made within the established tradition or correct theology of ancient tropes.
Frankly we probably dont need many new tropes for the Kyrie …
There are other places that could use them created, but thats not one of them.
Unless someone is familiar with the established tradition in latin, they dare not venture into this area of liturgical music.
I am in the process of putting most of them into english to the same melodies, with texts by some ex-anglican western rite orthodox monks for the anglican ordinariates.