He doesn't get in the way of the music. I think that the way he achieves that is by having total command of his instrument and vast musical knowledge. One can develop facility on their axe, but if they are concerned about anything technical while they're playing, then it will get in the way of pure creation. Of course a developing improvising musician wants to explore their chops. I know I'm guilty of riffage from time to time just for the fun of it, but that is not playing from a greater place.
Perspective is also important.
It's a natural tendency for a person to put their own ego ahead of the things that are important about creating music. The musicians who can make the music more important than themselves will have more chances to create something special. If you're familiar with any of the interviews with Keith Jarrett, you know he has a huge ego. But Keith is always able to put the music ahead of his own ego. This recording is a great example of playing with detached expression, recorded during the time that Keith has been dealing with Chronic Fatigue Syndrome.