I was thinking about this after reading Barry Williams response regarding Dupre's Op. 20 Variations on another thread.

So, what do you think?

For myself, I didn't have to work very hard to memorise most piano music. By the time I have learned the notes fluently, the piece is automatically memorised. But I have a much harder time memorising organ music.

Well I only memorize piano music. What I can contribute is that when I was without a decent piano for a few weeks recently I decided to memorize a new piece (a Scarlatti sonata) without touching a keyboard. It was very hard work, but it seems to be more securely memorized thatn any of the pieces where I first established finger memory through learning them from the score, and the experience of playing it is also different.

It's often said that those who sight-read well are generally less likely to be able to memorize than those who spend longer learning pieces. I can see some sense in this, although there are many people who seem to be able to do both.

I don't consider myself to be terribly good at being able to memorize. The only pieces that I seem to be able to memorize are pieces I learnt in my youth (when I couldn't sight read as well as I do nowadays and had to spend longer learning them), or pieces which I've had to put a lot of work into learning. But still there are a very few pieces which I'd be confident about playing all the way through from memory.

As for differences between memorizing piano and organ music, all I can really observe is that the organ also has pedalling to remember, along with stop changes and manual changes too.

I can sight read and memorise just fine on the piano, but not that good on the organ. But I also notice that organ music tends to stay under my fingers longer than piano music--probably because I practise harder and more carefully at the organ.