There is no doubt: sound comes first. The young duo sightread Rachmaninoff's Barcarolle this morning. Immediately it sounded wonderful, even when there were rhythmic meanderings between them. They were listening, that was the secret. Without knowing the piece they already had discerned its scenario, without any help from me.
I could not have done that at their age because my reading was vision-based, not ear-based.
I find that when I listen without a score I hear the music more accurately. When I read the score I pre-judge what I am going to hear and miss the instrumental subtleties that distinguish this particular version of the G triad from all others the world has ever heard.
Read this way a Beethoven sonata comes to life from within--right away.
This kind of learning, which admittedly takes longer, also lasts longer, both in terms of sustained concentration while playing and in terms of integrated fascination with the work.