Music could be described as going where the ear takes you. Listening to music being made up on the spot is particularly exciting if the improviser wants you to go along, to include you in the process of going where the ear takes you.
Too often printed music acts as an excuse to leave the ear out altogether, both that of the player and of the listener. I am fascinated by the difference between reading for sound and reading for the MuzApp notion of what is happening. I play with the score because that's what I do - also I do so many other things that playing from memory is out of the question, with some noteworthy exceptions.
The MuzApp notion is based on themes. Nonsense, say I. What the MuzApp people call a theme is one acoustical event compelling more acoustical events. Maybe they line up to produce a sort of idea that is easy to remember, but that is not what they are, nor is it why they exist (I am talking about real composers, not writers of tunes...)
As you may know I am a knitter. I no longer follow instructions but make things up as I go along. I am struck by how musical an exercise it is: the need for variation comes out of the string itself as it becomes too one-dimensional and I need it to cast shadows. I think of music constantly as I do it, music pure, not this piece or that.