I think I started messing around with improvised music about five years ago - whenever it was that I got my lyre. I spent a lot of time one Pennsic lying in the common tent in Storvik camp, brave enough to noodle around because there weren't many other people there and I thought they weren't listening.
I'm now pretty good with improv, to the point of being able to construct melodies with some degree of structure on the fly. The next place I wanted to go, performance-wise, was improvised text or text plus melody. I took a small step in that direction with "To War," a simple marching tune composed in five minutes on the battlefield at last year's Pennsic, the verses to which are all supposed to be improvised. It's simple - any seven syllables, or thereabouts, will do - there is no rhyme.
Yesterday, I spun out a ballad-y thing (I doubt the meter is actually ballad meter) for Spud, totally out of my head. It's still unrhymed, and I don't even try to advance the "plot" more than one line per stanza:
Little bitty baby lie down in the crib
Baby-o, baby-o
Little bitty baby lie down in the crib
Baby, oh baby-o
More Appalachian than medieval, I think. :) The melody for the matching lines also matches, now that I think about it. I even remembered the tune (also simple) today; yesterday, Moe asked me what song it was and was certain that I didn't make it up, but I'm pretty sure that I did.
It isn't Great Art, but it's another step toward where I want to go - and I think I made it because 1) it's fun to sing to the Spud and 2) Spud has no expectations. It's risky to walk into a bardic circle and try to compose on the spot if you haven't had practice doing it; it's boring to practice it without an audience. Spud is an audience who is entertained just by the sound of my voice, so I can flub without fear. Pretty handy.
We'll have to see if the boy likes alliterative poetry.