cantus firmus

For those who are not musicians and might ask what is cantus firmus, Wikipedia defines it thus:

"In music, a cantus firmus ("fixed song") is a pre-existing melody forming the basis of a polyphonic composition."

Or, even more plainly stated:

"The tune of the cantus firmus was taken from Gregorian chant; it would move very slowly underneath more rapid vocal or instrumental lines above it."

A musical textbook for form and analysis uses the work "Poplars in Spring" to give a visual analogy to the musical form concept:

"The poplar's trunk (detail to left) unites the ground to leafy canopy and sky above. The tree is analogous to a preexisting melody stitching the elements of a composition together. In music, we call this melody a cantus firmus. "

So why am I thinking about this now? It strikes me that it bears much similarity to my walk of faith these last few years. A place deep inside me hears that plainsong, that chant that is the core of my reason for being and being uniquely me. The more profound that trunk of revelation, the more it can get lost in an awful lot of branchwork. How many layers of counterpoint can God paint into my life before I utterly lose track of the foundational melody? It seems to be the question my life is about right now.

What's more, that form can be more broadly viewed as transitioning between A and B segments in a variety of arrangements. The textbook continues to draw analogies between the painting and the musical form: "Monet's detail to the right might be considered a binary, with sky at the top being part "A" and leaves at the bottom being part "B." The Lutheran chorale typically subscribes to an extended binary in which section "A" (called the Stollen) is repeated and followed by a section "B" (the Abgesang) which is not repeated. This AAB schematic is known as German bar form."

Here we get to the heart of the matter. My life does indeed feel like it glides through German bar form...with me being called to believe right now that the repeat of section A is closing and that section B will indeed commence. How will I receive the beginning of the Abgesang? Will I even believe that the Stollen could ever end? Or to use the painting's analogy, after my eyes climb 2/3 of the piece seeing branches, will they accept the trunk in a bare sky for the top of the work?