I'm teaching myself Clarinet again after a long layoff. I have been meticulously going through an "Essential Lessions" instruction book and have been making reasonable progress reading and playing in the lower register the past several weeks. Today I pick the clarinet up to practice a simple piece that emphasizes the A and Bb, looking to improve on these notes as they play thin and always seem on the edge of just breaking up. Today, they break pretty badly for me. Squeek! Squeek! - all over the place trying to do anything with the notes. I finally figured out that my embouchure had gone out as I had practiced my sax the day before. My angle was good, but the sides of my mouth were applying the wrong pressure. After fixing it, I was playing better. are these notes typically problematic?