work just on the low Bb. you need to play this low note with the “wrong” embouchure. something needs to be different with the way you approach it until you break thru and actually play an overtone.
also, can you play a middle Bb while doing the low Bb fingering?
That’s what I have been doing. Just the low Bb. I can consistently play the low Bb and then the first overtone and switch between the two with just embouchure adjustment. I cannot hit the third nor forth but maybe 1 time out of 10. Trying my very best to remember what I do. It’s just not “jelling” in my brain!
I amd using my “practice horn”, not my Selmer MK VI. It is a newly overhauled Buescher Tru-Tone C-Melody sax with a 1960s Brillhardt Level-Air mouthpiece withe a #3 Van Doren Reed. The horn plays perfectly, all notes up and down without ANY problems. I figured it I could master this on that horn it would be a breeze on the Tenor MK VI.