Just got back from my appt. with an ENT in Nashville who specializes in musicians. In the course of the exam he mentioned that a friend of his had done a study of what goes on in the oral cavity while playing brass instruments. The Houston Symphony brass players and other brass players who do not perform at a professional level were used in this study. One major difference that was noted is that the pro players play with their vocal chords wide open. Those who do not play at that level have them at least partially closed.