A good example of when I learned about songs having minds of their own happened some years back, when my daughter was a grumpy, teething one-year-old. It was close to Christmas, and I was up most nights walking the floors with her, trying to comfort her when her gums were aching.
In the wee hours of one morning, my sleep-deprived brain pondered the various Nativity scenes with the Holy Family, Baby Jesus in His Perfect Babyness, and Mary and Joseph the serene parents of a newborn. Hmph. I don't care if Baby Jesus IS the Son of God, He was also Son of Man - hence, He must have had colic. And later, teething pain.
My sleepless brain started to spit out this crazy song, "Rock dat Baby Jesus." It was about the REAL Nativity Scene, complete with smelly sheep and noisy angels keeping the Holy Family awake at night. Silly, yes; but it helped me to smile a bit during a very trying time.
The next morning, after a few hours of sleep, I sat down at the computer and started typing. My unconscious mind had been busy while I was asleep, and I knew when I got up that I had to write this silly song. But what happened as I wrote was that this silly song began to change as I wrote. It became a lullaby, sung by a very human mother and her love.
Later that evening, my husband and I were getting ready to go to a Christmas party, and it hit me while I was getting ready - I already had the tune for this developing song. I had been singing a wordless "la de da da da" to my daughter over the previous nights - and with some tweaking and reworking, it fit perfectly. The song became "Rock My Baby Jesus," and you can listen to it here. (If the link doesn't work, go to http://www.women-at-the-well.com/music-1.html and click on your choice of the high-speed or low-speed modem.)
Babies (usually) wait until they are ready to be born. So do songs.