The Tao of Jazz Improvisation by Sheldon Zandboer

There are thousands of subconscious calculations occurring continuously and instantaneously during every musical performance. For instance: time, tempo, feel, key, mood, etc. If we can automate or internalize the majority of the fundamental elements, they become less of a burden on the player. The solution is to train yourself, such as a martial artist would: to react instinctively to your musical "environment".