I am writing this in the blog to post in the forum (because somehow there's danger of losing my writing if I directly write in the forum) where currently there is a discussion going on about ninefold Kyrie.
Since we thankfully still have an 'option' to have ninefold Kyrie in Novus Ordo (GIRM,52), children's schola sings ninefold Kyrie. I have a couple of older boys starts the first Kyrie eleison and sing the alternating parts by themselves, and the rest of the schola sings with the congregation. Also in the leaflet I hand out to the congregation for the Latin text and translation, I type in bold the part that congregation sings with a short explanation under it, something like (9 fold Kyrie, sung in alternation with cantors, please join in bolds) - hopefully they will know it without this explanation when they get used to it. I also told them about the tradtional structure of Kyrie, 3 times to the Father 3 times to the Son and 3 times to the Holy Spirit, and also the nine choirs of angels around the altar. A lady I know who likes contemporary music and happens to be in the Mass when the children sing, asked me later why they sing Kyrie differently. I told her briefly about the tradition, and she was amazed saying " there's so much in the Liturgy..." This was a chance to share our Catholic faith through traditions in our Liturgy, even if it was a just a small part. (I think it's a good idea to have a corner for "Note about Music" in the church bulletin where you can provide interesting facts about music, explanation of a neum per week and so on.)
Musically each Kyrie eleison of Gregorian chant has its own unque ternary form that fits the texts beautifully. While trying to make it easy for the congregation and aiming for the immediate result of their singing, 6 fold is destroying this beautiful form of Kyrie. When our Holy Father talks about the beauty in art and music, he emphasizes the importance of the form. When we sing 6 fold Kyrie, we are giving up this beauty for the sake of convenience. In order to experience the divine beauty and love, there must be some sort of sacrifice and effort on our part also. If we keep seeking for our convenience and easy way to worhsip God, what are we going to have left in our worship?
If you wish to dare to be a bit 'extra ordinary' and inpire the congregation to sing and experience the beauty even with the simple Ordinary parts, there are ways to do so (although it might take a long time and hard work). One of my children's schola, which is now getting used to ninefold Kyrie, asked, "why adults sing only 6 fold Kyrie?" Hmmm, don't have a good answer. (Maybe it's too hard for adults or are they too busy? I don't know.)