St. Patrick's Breastplate

I have been engaging in an interesting attempt at memory recall this morning at work. On Sunday we sang a hymn called St. Patrick's Breastplate, which is our second time singing it. The first time was a disaster, because the hymn is very complicated (compared to most standard hymns), especially if you aren't familiar with it. This second time it went a little better, but I can't say I sang it quite perfectly, even by the end. Now this morning I started to think of a measure of the melody. As I hummed it, it brought to mind the next part. After a few tries, I was able to physically reproduce that with my vocal chord vibrations, which seemed to set it more fixedly in my mind.

This in turn made me realize that the first measure that I had remembered was similar to the song but not quite right. I assumed I had hit the wall there. But as I was working, it suddenly occured to me how is should sound; once again, it took a while to reproduce physically. This process continued until I had reconstructed the whole melody. Yet immediately after I had sung the song with the congregation yesterday, I had been humming it and couldn't remember the whole thing! I even tried for quite a while. How then could I remember it today? It appears from this that it is possible for one to recover a truth or an actual thing more correctly or completely given time to dig into long-term memory (?) (mid-term memory?) compared to the immediate retrieval of short-term memory.

Of course, I'm not completely sure my final complete memory of the song's melody is correct; I believe it is, because it arose into my mind wrapped in a certainty, an authenticity I could not naturally doubt, though of course I doubt it intellectually.