I've heard from almost everyone that ideally you should play with no mouthpiece pressure ...Um, isn't this physically impossible? The vaccuum created by the pressure makes the buzz possible in the first place, right? Do they mean, "not excessive mouthpiece pressure?" Because my trumpet teacher (has a PhD) says that it's all bologna, and mouthpiece pressure is totally normal and necessary. And even that the longer you play at once, the more you will use, and it should be so. Thoughts?