There is no such thing for a trained musician as "simply to listen." We cannot do it.
Once we have learned the grammar of tone function we are like Adam and Eve driven from the garden, in this case, the garden of auditory delight.
How did I learn to simply listen? I set myself the task when I first began to teach in the 1970s: I would listen to students without looking at the score. This would require of me that I hear as they heard, not as I thought they ought to hear. The difference is both huge and fascinating.
Among the more memorable lessons I took away from this experience was of how certain composers made it a central feature of their work to focus attention on the shifting of resonance from one instrument (say, the piano) to another (strings, or winds). My first overwhelming experience of this was through listening to some Mannes Prep students learning a chamber work by Robert Schumann. I came to realize that the point of the piece was not so much to get the strings to play in tune with the piano as to have each different sound-source become a potential resonant partner with the other.
Later I realized that Schumann was merely spelling out what he had heard in the music of Beethoven, Mozart, and Haydn.
