Im a returning player, having taken a 20 year break from the horn. Now I’ve been doing MTM for the last year or so and self diagnosing and working through stuff and filling my head with all sorts of concepts and knowledge. I’ve been able to move towards a more relaxed technique or what I at least perceive to be so. At times I sound great and things seem to be going in the right direction. However, I sometimes re-gress and find that I get ‘inteference’ in my sound as I ascend, this despite maintaining an open aperture, bringing in my corners and forward arch on the toungue. It sounds as if my lips are in contact and Im getting unwanted overtones. I play on a Bach 1.5 C and on placing the mouthpiece and doing the mwaoooo drop my jaw whilst still retaining upper lip in the cup. What is going on?