When I sit down to compose a song, I most often start with a memory or feeling. It works best when that memory is multisensory, synaesthetic and engages emotions. Usually there are a variety of related "sense anchors" that I can dive into many times during the writing of the song, that don't wear out, in a repeated process like re-inking a pen.
I haven't been able to go back to decades-old, unfinished songs and make anything out of them. I think it's because my memories have drifted away from the sense anchor that I used to write it. When I try to fix part of the older lyric, I always patch it with the wrong material, they become eclectic and weak. That is true for both the words and the music. And the original sense anchor is no longer available, not having been correctly summoned when the song was first attempted.
Giving the sense anchor form is the reason for composing a song. It is to bring into existence a form that, as a stimulus, allows me to lock into this temporal world a way of experiencing the sense anchor as an explicit thing. Not that the thing is the explicit subject. The subject of the words, and the compositional strategy for the music combine to cause in me the art experience. What I am able to do when I compose is arrange things in this earth so that they provoke something not of this earth. Medium, sense anchor, and experience: composition by triangulation.
The sense anchor doesn't have to be a memory of something I did. It can be from a feeling, a cadence, a shape, a rhythm of words. In formalism, the sense anchor can come from a compositional strategy. But throw in too many formal elements and the sense anchor can't be felt because the music becomes dilluted.
To the degree that a sense anchor is shared, the music is tribal. To the degree that a sense anchor is unique, the music is avant-garde (anyone park their work next to that word now days?). I like music that falls into both categories, but since high school have always liked Michael Snow's remark to the effect that if you're going to make something, you might as well make something that didn't exist before. And the act of giving something a physical representation in this world that is otherwise ineffable , this reminds me of Gabriel Vahanian's remark that the "word" is iconoclastic only as it makes man become what he is not, that is, man instead of God.