Sorry I am not able to comment on the origins of jiu jutsu as I have never studied it but I do agree it seems to combine teachings of both armed and unarmed combat.

What kendo has taught me is a modicum of patience which I am trying to apply in re-learning music and how to play the whistle properly.

I know I have to practice and work at exercises in order to make those darned fingers do what I want them to do, in order, in time and without stuffing up. And at the same time I am trying to learn tunes and make them work naturally and I want to sometimes rush in and try to use some of the techniques for ornamentation. Then I get the big step backwards as I once again stuff up. then it is time again to break it down to slower more practiced movement again and try and go up another notch.

I am amaized by the coordination foe example that box players exhibit. Push, pull, play with both hands at the same time. In fact watching anyone use two hands plus coordination to make any instrument look simple to play makes me admire the sheer practice and time put in. The more economical and simple it looks the harder I know they have worked. Just like good martial artists.

And I guess that just like good martial artists a good player gets that buzz inside from making a difficult passage of music sound natural and free flowing and moreover they add their own stlye and signature to the music. And when they have done it they still think 'could I have done better'

An old Japanese saying was 'After the battle retye the helmet'