I think I’m experiencing this a bit right now and understood part of it earlier on in the course.
I’ve been playing on a shallower mouthpiece for the past week or so, a Bach 3E.
It seems to me that playing on the shallower mouthpiece might be forcing and/or helping me to learn more about sympathetic buzz vs synthetic buzz–it seems like a very subtle difference results in my range / sound cutting off past a point on the shallow mouthpiece, whereas playing on a deeper cup (i.e. 10 1/2C, 3C, 5C, 7C, etc.) perhaps allows me to manipulate a bit more with my embouchre/lips and protrude into the mouthpiece without cutting off.
Today, I kind of had an epiphany that I think I was subtly tensing/flexing my lips (top to bottom or upper pushed to lower), rather than minimally tensing the corners and allowing my lips to vibrate as freely as possible, not to mention backing off the air.
For me, it seems that playing the shallower mouthpiece is helping me realize this more and preventing me from trying to go higher by blowing harder or manipulating my embouchre (too much).
Before, I was happy with my progression–I was up to an F above high C but then I stopped there and kept catching myself manipulating / kicking with air beyond that point. And I didn’t like the fact that I couldn’t play the shallow mouthpiece; it seems that the best players can play on just about anything and can somewhat switch between.
I don’t know for sure that playing on the shallower mouthpiece will help me move to the next level, but I believe it will. I think I’m learning more about what is helping the sound resonate more.
My range actually feels a bit lower and less secure as before when I was playing on the deeper cup mp’s, but I notice that I get up above the staff without even trying–I get up there quickly / easily, I just catch myself overblowing and pinching.
When I focus on relaxing / not caring if I hit “the note” , backing off the air and just try to play freely and open, it feels somewhat effortless.
I also noted that I am playing higher than before when I pull the horn away from the mouthpiece to see if I’m buzzing “synthetically”.
And my sound on the 3E is much better than when I started playing it originally. I actually feel like I can get a nice warm almost dark sound if I focus on it, or I can make it bright / loud / shrill if I give it more air.