Well, it's not so easy. We can't just say that musu
means create, give birth, and use its western language meaning in the concept.
Arts of war don't give birth, but quite the opposite: they kill people. So, the word must have been used in a symbolic way, not intending its "root" meaning.
When I use "improvised", this is a western concept that does not seem to have an obvious Chinese or Japanese counterpart. So, somebody implying a similar thing, would have to find his/her own Chinese/Japanese word for it. That word could very well be musu/umu
I mean improvise in the jazz musician way: melody created in the moment, so to speak out of nowhere. This is creativity in action.
I believe that is what Osensei was talking about
: Using the aiki
principle for creativity in Martial arts. Like Charlie Parker on the saxophone
is the song, aiki
is the theme or sentiment, musu
is the creative process.