Thanks for the replies!

Chris – I also notice the same issue where playing louder can cause the note to split. It’s an odd feeling that I also notice occasionally when trying to slur to the next harmonic; instead of the pitch changing, the volume does and with it comes the double buzz. This only seems to happen on bad days or for part of a day. I have also noticed that when the note splits I can feel air escaping from my nose, presumably a result of pressure change, but I have also wondered if it’s part of the cause. Glad to hear it’s not just me and it’s great that you are improving, I hope that trend continues!

Ronald – Thanks for the feedback and the photos, it’s really interesting to see the difference. Although I may have slightly exaggerated the setting in my photos to show the shape of the upper lip, I have certainly been playing more puckered than you. If I use a similar setting to yours, the protrusion is much less noticeable. This also ties in with Greg’s video about not playing “in the red”. I was possibly taking the “mmm-aah-ooh” thing a bit too far when it is intended just as a tool for establishing the feeling of the corners. I have just spent a bit of time playing with the lips less puckered and although my sound needs a bit of development, it’s more consistent across my range with no double buzzing. I’ll keep at it and see where it leads me. Thanks!

P.S. Here’s my new high C: