The brain working over-time is an issue that I do battle with.

My brain (and I’m guessing yours) is working all the time… and should be working all the time. It’s the thing that stops us doing ‘mindless’ auto-pilot nonsense. I think I know what you mean, but the problem isn’t so much the brain or mind, but the devil-on-my-shoulder (call it the critic, the nanny)—the entity that always second guesses choices and gets in the way of a decision.

Could it be nerves?

Funny thing is, I’m actually almost certain that wasn’t the case: I felt pretty relaxed…

This is something I go through sporadically. Some new context or stimulus that I’m ill prepared to deal with. I agree, this is how we learn (change and mutate) as performers, as improvisers, perhaps as people.

If we look at improvisation from a social point of view, is it that maybe like the way as humans we develop as we mature and wisen, that once again your improvisation technique and views are once again re-developing. They do say that we are always learning or re-learning. Or another way to look at it is Religion: one’s religion
Personally I found the duets between you and Franziska to be intense (in the positive sense of the word) and inspiring.