Trombonist and composer Normal Bolter has produced some YouTube videos where he discusses the vertical and horizontal aspects of musical phrasing. As I mentioned a couple of days ago, we often have a tendency to evaluate our practice on an objective level (correct notes, in tune, etc.) rather than the more subjective musical expression. Good technique is extremely important for a musically satisfying performance, but we also need to practice expressive playing.
What makes playing expressive, though? Bolter discusses this question, using Morceau Symphonique by Philippe Gaubert and a Rochut Melodious Etude as examples. You can check it out here or on his blog.