If you haven’t got it close to memorized, you probably haven’t got it well-learned.
I often say to my students, “the only way to memorize something is repetition.”
I truly believe it, but I think there’s an interesting corollary.
The only way to really know something is to practice it enough that it’s memorized. The amount of time something takes to memorize is roughly equivalent to the amount of time it takes to do it well.
What that means is that when my ensemble sang through a piece this afternoon, I knew it was close to memorization, even though they hadn’t sung it “from memory.” Their work at learning the difficult parts had already covered most of the ground needed for memorization.