Flow happens, if I am performing and can't get to the 'Flow' aspect, it's a bad night.
However, as mentioned, practice does indeed help make the 'Flow' possible, but to me that went without saying.

A musician knows how to play their instrument (or 2 or 3 or 4)
A musician getting into the 'Flow' was the article, and yes, it happens. You know the music well enough that you are not in the 'reading/thinking/computing' state of mind (learning), but more in the feel/groove state, which is always a much better place to be.
Music flows out of you that you never would have anticipated sometimes.

I do not work here, but the benefits are still awesome
Make your sound your own!