Hello - I am not sure what anyone can suggest except - "practise more" but I thought I would ask anyway. I am learning a piece where the rh plays octave stretches for quite a while and I just can't seem to do it. My hands are quite large and flexible and span more than an octave so I can't keep them fixed to an octave for very long - and then it all starts going pear-shaped! Any tips?

I think you need to know why your hand is not consistently making the octave cleanly. Are you randomly hitting 7ths and 9ths or is it all 9ths? Is is just white note octaves or black note octaves as well? Is this just sight reading or playing normally with music? (I'm assuming it doersn't happen when playing from memory as you could look at the keys to control your fingers)

If you have fairly big hands, then when you are first learning, there will be a 'convenient' period when you can accurately place octaves because that is the maximum your hand will comfortably strecth too. In other words you achieved it by simply stretching as wide as you comfortably could. Now that your hands have developed and you can reach 9ths and maybe 10ths, you have to use a more positive method of control of the span (the same method you use to produce spans of less than an octave).

The good news is that it improves with practice. It is probably worst with C major, where you dont have the occasional references from the black keys. You can sometimes give your fingers a reference from the black keys, by playing more forward on the keys; this helps to keep your fingers centred and they are less likely to drift apart or together.

Mole

Is it that your hands are getting tired with the repeated octave stretches, ie you are OK at the beginning and then things go wrong? Practice will help with that - building up stamina.

However, if you are missing the octaves consistently, you need to train your brain/hand to the right stretch - again, lots of practice - but rather than sitting down and playing millions of octaves, I would suggest playing an octave every time you walk past the piano. Put a couple of pieces of masking tape an octave apart on your desk or any other convenient surface and do the same - you will soon learn the right interval!