First off, thank you all for your answers.
I'm not sure how to define Musical Discourse, in Portuguese "discurso musical" (which I translated literaly) would be immediately understandable. Maybe, to define it as the flow of musical ideas/textures would be apropriate, but I am not sure.
Albert Pensive, let me give you an example (however acnowledging that this is a very subjective matter). Take "Le Marteau sans Maitre" by Boulez. Boulez uses mostly a serial language in that work. However, a diferent treatment of that language can lead to extremely diferent results. For a long time I didn't listen to the full work, because I didn't like the way it started, as the first movement is pretty chaotic (or at least it souds pretty chaotic on the first listenings, so one could say it is not really accessible). However, the second movement, is completely diferent musically, and I though it was very beautiful from the first time I listened to it. I think that the main reason for that is the rythmn. In both movements the language is serial, but the rythmns used in the second movement are a lot simpler and you can sense a pulse. So, to make it short, the language is similar, the treatment of the language is diferent, and thus, the flow of the discourse is very diferent in the two movements, and one is a lot more accessible than the other, i'd say :-)