You haven't said how long you've playing. You need to be fair to yourself and if you've only been playing a short while then you may be using reeds which are quite light e.g. strength 2's. If that is the case you might find that your intonation - general tuning is good up to a middle G but terrible when you start playing up to D's on the second ledger line. Patiently play slow and long semibreves across the whole instrument until you can notice the pitch of each note you play not waver without your control. After a little while go to strength 2.5 and then strength 3 reeds.
If you have been playing a while - the answer is still the same but with obviously stronger reeds. For really fast development try blowing overtones. Pitch a low B or B flat and without using the octave key play and octave up, then a fifth above that, then a fourth above that so that you are playing the notes B flat, B flat, F and B flat.
Stay blessed - KennyBB
