i dont' think one should worry about "body movements" - some are needed for specific purposes! and if you don't think at all "oh, i should stand still" or "oh, a big body move back and forth wuld look pretty here", then you won't move more than necessary.
in music it's very very important that everything is natural - including body movements (imho)
I agree with anda for the most part. I will say though, that at the close of a very enthusiasitc piece it simply warrants a fast stance.
Here are my thoughts about this all...
Body language is communicative, as we all know. I don't think that we can entirely divorce ourselves mentally nor physically from this, nor should one try. An actor thinks very much about how his/her body will portray what is to be communicated, yet all for the purpose of the character and the story, and we as performers are indeed actors (to a degree). I think that we think about how we move our body, without thinking about it, LOL

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The most important thing here to me is that one is fully engaged with the music both mentally and physically at all times (if possible). When music swims throughout the depths of one's soul, it is nearly impossible to
not move. Music and its components are meant to move us, this is entirely normal and natural. Resisting is not natural.
Perhaps there is a line though, where it becomes too much. I for one do not know what that is for eveybody, I only know this for myself and I can feel the difference within. I will say though that I have seen some pretty entertaining stuff, of which I have not completed my opinions about because ultimately it is not really my place to decide for others what is too much for them.
As you have probably noticed already, even listeners like to move a little. Some try to communicate to the rest of the room that they are "knowledgeable" about this and that and the other thing. Some listeners communicate that they are too proud to be moved.
When it all comes down to it, I just like to hear and see somebody believing whole-heartedly in, and caring deeply for what they are doing and boldness in
that is not a crime.
m1469