I'm currently practicing my overtone series and trying to get a play some altissimo. Right now, I've been able to play up to a D7 using Sigurd Rascher's Top Tones for the Saxophone, but the notes are incredibly sharp to the ear and unpleasant.
Is this something more long tone practice will help, or is it the overtone practice because I can only really get to the 4th or 5th overtone on Bb, B, C, etc? I'm concerned because I don't want start a habit wrong because it does seem like I'm straining a lot on the higher notes such as C7 and I can never go above D7, which seems like an overtone issue. What is the more efficient way of practicing to increase my tone and make sure I'm not practicing my altissimo wrong, and would you suggest I get more done on my overtones before transitioning to altissimo?