I'm beginning to believe, more and more, that good improv skills are critical for a modern medieval musician to cultivate. I don't mean to go out and learn jazz (although that might help), but to play enough medieval music that you get the sound of it, and then can improvise simple, similar-sounding music at a go.
In particular, I've been thinking about it in the context of dancing. We know darn little about early medieval dance, is my understanding. But from what we do have, both in contemporary reports and later surviving choreographies, seems to indicate a certain language of music and dance.
Consider that the estampie dance tune form calls for performers to improvise verses. That's right - the dancers don't know how the music's going to sound. But they do know that it'll be eight bars, or sixteen, or what have you.
Consider how simple it could be to improvise very basic choreographies for line dances and round dances. Two slips left, one slip right. Two slips left, one slip right. Repeat, repeat. Put it in a line and extend the pattern to eight or ten steps and that's a pavane, isn't it? Or a verse-chorus form along the lines of the English country dances. If everyone knows the building blocks, it would be fairly easy for dancers to invent new patterns. And if the musicians are well-versed in improvisation, they just need to be told the pattern and can accompany it:
"We need a verse of eight bars and repeat and a chorus of sixteen bars and repeat."
"Give us a minute to work out the basic structure and we're good to go. I want soprano recorder doing melody on the chorus and harp doing melody on the verses. Verses: Drones, I want home-away, home-away in Dorian. Got that, harp? Let's use... I don't know, a falling figure from 4-2-1 as a primary theme and cadence. So we end the verses with 'away,' so chorus: drones, we bring it back home for four bars, then..."
First verse through, harp probably plays exactly (let's say in D Dorian) a pattern of half-quarter-quarter:
Just to, you know, get it down. Then, as it gets into the fingers and gets boring, the ornamentation and variation can start. Maybe that last line can go A-F-E, A-B-C up, to lead into the chorus on a rise. Or instead of the repeat being exact, the away pattern could go down to F-D-C. And notes start getting divided, grace notes tacked in. The melody expands and takes off.
Simultaneously, the dancers are surely acting in parallel, ornamenting the basic steps with elegant sweeps of the feet, or turns of the head and torso, or other such things that I've seen but can't duplicate myself. Suffice to say, good dancers know how to ornament a dance without disrupting its basic steps.
You could do this. I think it might be fun.