Reappearance in a painting of earlier images, forms, or strokes that have been changed and painted over.
So I started seeing (or was that hearing?) the music we were working on in the studio in terms of that definition. Seeing it in terms of a painting with layers and touch-ups and start-overs with new layers that get erased in places that let the underlying pattern come to the top and be seen (or heard).
This is what metaphors do - they let you see (hear) things through the prism of another art or through the walls next door.
Note that "the Arts" are often spoken of in this collective way that tends to make them all the same - obscuring the fact that there's only one of "the arts" that comes exclusively through the ears.
Most of the world is listening to music in terms of forward flow - based on where the music is "going" and "what comes NEXT." But there's another angle: Vertical listening is about listening to "what's happening NOW" - letting your inner ears scan up and down the sonic spectrum, asking what kind of "shapes" you're seeing, then noticing how that picture motphs as the music moves through Time.
Robert Irwin's subtle art installations are based on what he calls "perceiving yourself perceiving." Vertical listening is related to "listening to yourself listening."
So this is where the title "Listening to Pictures" comes from: The process of vertical listening creates the picture.