Memorizing
My favorite rant of all times is on memorizing. For one thing, I
never call it playing from memory - always playing by heart. I think
the heart is very important in all of this. I actually believe that
it is what you like about a piece that affects your interpretation
and therefore the memory of a piece. One reason I like using my
memory is that I like to play by ear. I call it playing guitar with
your ears. In fact, they say perfect pitch is a function of memory.
I have passive perfect pitch, which means I don't writhe in agony
when somebody isn't exactly at a = 440. This can be very useful when
you are playing at baroque pitches which are a = 415, etc. also when
you need to be late at a rehearsal but you know exactly where
everybody is because you know what key they're in. I like my kind of
perfect pitch, and actually developed it by realizing what the
lowest note was that I could sing. I also listened to a lot of
Segovia records, and started finding that I could hear the open
strings, that I knew what note the next piece would start on. Later,
that I knew the whole piece by heart, and then one day, I sat down
and figured out The Old Castle by Mussorgsky without the music, just
from the Segovia record. My idea of fun, really. Kept me off the
street, anyway.
Maybe because I learned pieces by heart by listening to them on a record, I have a total aversion to learning pieces by heart by going backwards one bar at a time. I think that is a great way of solving technical problems, and I just loved when Paul Galbraith talked about whittling down technical problems to two or three notes in a masterclass he held here. But for me memorizing a piece is to understand what is going on in it (to know is to love) and for that one goes from the beginning, and sees how and why a piece is built up the way it is.
One thing I really like about playing by heart is that it is a chance to rediscover a piece by ear. One hears the finesses of what one would like to bring out. One is also a lot freer to listen to oneself and look at one's hands if one needs to. I think it is a good idea to be able to sing the melody if one freezes up in the middle of trying to memorize a passage. If you can sing it, then you can play it by ear, so there is continuity in what you are doing, and then the fingers will remember the other notes around the melody. Never bite off more than you can chew. Learn pieces by phrase until you have a whole section down. Even learn it one articulation (mini-phrase) at a time.You'll develop a sensitivity for the fine points of the piece that way. Learn it by playing, not by looking at it. Play it until you really like what you hear and see. One reason I play well by heart is that I kept correcting technical errors while I was practicing, and suddenly, I knew the piece by heart!
Obviously studying a piece by looking at it has great merits too, but maybe not in conjunction with learning a piece by heart. On the other hand, if you are sitting on a bus, doing nothing, that's a great time to run through a piece in your head.