So about a month or two back, I was sitting in with my teacher and working through some exercises, and at one point I was getting poor intonation on a note, and he said, "Try tightening the corners a bit." Apparently, my subconscious Neanderthal brain latched onto "tighten the corners", and I started making it a point to keep the 'corners tight' when doing all my exercises since that day, and especially as I play higher. Coincidentally, I've been experiencing significant inconsistency in range, tone, and endurance over the last several weeks, and my embouchure often fatigues easily. For example, I'll be playing Clarke's or Arban's studies, and my embouchure feels fatigued and out of sorts when I get near the top of the staff, and soon I reach the point where I just need to give it a break. At that point, my gym-rat brain thinks, "Alright, you gave those muscles a good workout! Now get some recovery time, and you'll come back stronger!" Hasn't really happened yet, and this morning as I was working through exercises and doing some serious introspection, it occurred to me that I very likely took my teacher's comment completely out of context, so I started thinking about corners and aperture. As I try to play higher, I've been trying to visualize tightening the corners. It occurred to me that as you play higher, rather than think of tightening the corners, the concept should be 'focus the aperture' - it should be something that happens concentrically, not just on the sides. As recently as 2 weeks ago (roughly), I could play up to about an E or F above the staff, and my embouchure felt almost relaxed through the B,C,D and then started getting a bit more strained towards the top, but overall, there just wasn't that much effort required. This morning I tried to hit a B above the staff, and everything bulged and strained, and it was very obvious that I was Doing It Wrong. I've been working very diligently on doing proper exercises, good technique and breathing, consistent and intelligent practice, and yet I seem to be going backwards of late. The only thing I can think of is that maybe I started jacking around with my embouchure unproductively. Am I onto something, and is that visualization of focusing the aperture a good one? BTW, I'll be getting together with my teacher again next week, but he always encourages getting other perspectives, so would this collective cornucopia of trumpet wisdom please feel free to sound off in the interim! Me asking for advice on this forum is in no way a reflection on my relationship with my teacher. On a completely unrelated note, Bryan Adams just cropped up on my laptop singing 'Summer of '69', and that's darn good listening on a Friday morning. Make it a heckuva good Friday, boys! ......and girls!