Another Night at the Craft Fair - the Challenge of Thinking in Music

The second evening of playing went even better than the first one.  I was more relaxed, but I was still playing with the intensity that comes when you play in public.
Improvising music is one of the most challenging activities I know of, and I'm not sure it gets easier as you improve at it.  Obviously some aspects of it do get easier.  You know the songs better, so you don't have to make an effort to remember them.  You gain in confidence, so you have more control over what you're doing.  You develop familiarity with chord patterns and rhythms, so you're not baffled by a half-diminished chord or a minor major seventh.  But the closer you are to mastery, the more you demand of yourself.
In the beginning, when I was struggling to improvise at all, I was glad when I just managed to follow the harmonies and begin and end on time.  I still get lost occasionally, but usually I know where I am in the song, and I'm working on playing interesting riffs, coherent solos that build, giving variety to my playing - so things aren't really any easier.  On the contrary.  It's harder for me to satisfy myself.
In some moods I think that it's too bad I came to this rather late in life.  If I'd learned as many songs and known as much about jazz when I was a teenager, I'd be struggling less now.  On the other hand, it's amazing that in my late sixties I can do musical things that I couldn't imagine doing ten years ago.  It's important to grow at any age.
Playing a fast-moving sport like tennis, hockey, basketball, or soccer probably demands concentration of a similar kind, though, never having been much of an athlete, I'm only guessing.
What it takes is thinking in the language of music as you play, the way you think in a language as you speak. 
A few years ago I took a course in musical cognition at the Hebrew University, and I got a lot out of it, though I think I barely scratched the surface.  I know that there are people with high musical aptitude, the way there are people with high mathematical or verbal aptitude, who hear, retain, and imagine more than ordinary people.  My own musical aptitude is high enough, I guess, for me to imagine what it would be like to have the extraordinary musical gifts of a great musician, and that's a positive thing.  But when, for example, I read about Shostakovich, sitting down and writing out the score of a symphony that he'd composed in his mind, without trying anything out at the keyboard, I am infinitely humbled.
The intensity of improvising in public (not that there was ever a big crowd listening to us) for a couple of hours last night took me a little closer to the state of musical awareness that a truly gifted musician has.  I could barely sleep last night.  Music kept running through my head, the tunes we had played, and musical ideas of my own.  The intense attention I needed while we were playing stimulated my brain.
Ordinarily I hear music without listening to it as carefully as I do when I'm playing.  Maybe it's a defense mechanism: if I always listened to music that carefully, I would be overwhelmed by it, and I can't really afford to be overwhelmed by it.  There are so many other demands on my life.  But I welcome occasions like these, which give me a glimpse of a higher musical plane.