As has been said above - very interesting topic.
I'd just like to add a vote for the "sequence of nerve impulses" idea.
As an aside I love playing from memory as I can then focus more on the music, but although I can memorize and prefer it to the torture of sight reading (and am really pleased that I now have the 1st movement of Moonlight always with me - and me just a grade 4
) it does take a frustratingly-long time (3 years or so to get the notes and fingering of Moonlight and memorize - but I had technique to learn too).
Anyway - since I was first taught to practice always HT (for which I'm grateful), I've found that it is the totality of the "current state" that triggers the memory of the "next state", i.e. somewhere there seems to be a map of the piece laid out as a sequence of configurations, and if you subtract from the sequence by removing one hand, it becomes really tough if not impossible to play from memory.
For these reasons I much prefer nowadays to approach a new piece HT from the outset, unless really really stuck!
Hmmmm.... I wonder if "memorizers" tend to prefer HT and "sight readers" can do HT or HS equally freely?
QUOTE(LooneyTunes @ May 9 2009, 07:52 PM)
The aural cues must have a significant role too. Perhaps the brain needs the aural cues from BOTH hands as an aide memoir?
Definatelty; I've found even playing a different piano can disturb the memory, and have you ever tried playing from memory on a keyboard with the volume turned off? :-)