I was just playing a Bb Concert scale two octaves this evening, and I realized that my abs were doing a whole lot of work. I knew that the diaphram was a big part of the mix but this surprised. All my core muscles tightened up as I got higher. I was not straining at all for any notes and I was using (what sounded to me) an excellent tone, so I wasn't pushing myself note-wise. Is this alright?