I have to admit, I have not read all of the thread. However, it is quite an interesting subject. Especially, since I recently discovered, how people differ from each other, even family members playing the same instrument.
First of all, I would say that it is not important to learn how to memorize.
QUOTE(sbhoa @ May 14 2006, 06:48 PM)

I don't know if it's true but I get the impression from my rather limited experience that the real high fliers are natural memorisers anyway.... though the reverse is not necessarily so.
Maybe it is something to do with the way that they relate to music generally?
I think, this comes with the process of learning and has little to do with high fliers. Once I start on a piece, I usually know neither melody nor notes. If the piece is important to me, for whatever reasons, I start practicing it. With metronom, without. Some passages I can do, just because they remind me of arpeggios, or scales, or whatever. Other passages are easy to memorize because the tune is such an earworm. Then there are passages, I have difficulties with (I play flute). Fingers not synchrone with each other. Bad tone. Or I just simply cannot remember what is next and if it's a fast passage, my fingers just stumble over each other and I have to start the passage or the piece all over again.
During this process, I do several things. (i) I get to know the melody, even if it is not a very harmonic one. (ii) My fingers learn to memorize, what comes next. So, even when my eyes are not fast enough in those difficult passages, I can concentrate on the passages where it is likely I get thrown off course. And by the time, I play all parts to my satisfaction, I found that my father, who has the very bad habit of stealing my notes from the music stand or to go through their pages, while I play, is not able to stop me from playing, even so the notes are not in front of me anymore. I have yet to memorize a piece on will completely, but there are several, where I tried to play them as far as I get from memory, and I almost came though to the last line of the music sheet.
However, my uncle, who is a much better player, and has had much more time to learn the pieces I play, says, he is not able to do this.
For me, this leaves one conclusion: there is no need in the early process of learning an instrument to learn memorizing, unless maybe there is a known problem with that particular task. Even so some pieces might be considered standard repertoire, the skills simply lack in the early years to give a piece, however easy it might seem, the full meaning and purpose. (And an ability it really is that needs to be developed - but there are other sings to help there like poems, lyrics of a song or whatever).
I agree with the several statements, that the emphasis and feeling increase with playing less dependently on the written music. There already is a huge jump from playing with metronom and without to add emotions to a piece. And the more secure a piece is played without a dependency on the notes, I believe the quality and feel of the piece will gain even more. I think, by the time I reach professional level, there is little need to memorize anything of the things, I studied so far. And the new pieces will undergo the same procedure with the same result in the end. Maybe, that will be the point were I - on will - will memorize some turns where I loose track of the melody. But considering the ease to memorize that comes with practice, I will worry about that than.
What I consider important is the ability to sightread. And that is what it should be about in the early learning stages. A musician can play almost anything from sight, when that ability was developed fully. Which will be very helpful in the end when it comes to expression and correct playing.
QUOTE
...desirable, but still not essential...my current teacher is a concert pianist but not a natural memoriser and does have the music when she performs - but she's not actually reading it, only using it at certain points - I suppose for tricky passages, orientation etc...
That same statement could also come from my teacher. She says there are pieces out there, where even a James Galway would not play from memory, because they are just so difficult and unforgiving. (Not, that he would play such pieces in the first place, since most of them are not soloistic). But I certainly understand it, that the notes are just used in such cases as an orientation.