Piano Forum

Ah, I've been frustrated so often by this very question. The answer, while frustrating, is that whether or not a piece is most appropriate for your current level of development is whether that piece allows you to improve close to "optimally". That is, the piece should teach you new things (not too easy), while not taking an inordinate amount of time to do so (not too hard). Often learning 3 moderately difficult pieces in sequence can increase your rate of progress faster (and might be learned quicker) than learning 1 difficult piece.

Also, in addition to technical development, there is the aspect of increasing learning efficiency. Every piece you learn up to a good standard increases your efficiency at learning new music ever so slightly. You see the patterns better, you make more sense of the musical direction, you use all kinds of things which you've understood about music to speed up your rate of learning of a new piece. You also have a much better idea of the amount of time that it might take, and can pace yourself better.

I would suggest having a teacher who can really guide you through this. What's difficult is that there are so many stages of having "learned" a piece. Even if you can play it note perfect, the technique might be producing poor sound quality, or might be tense. Musical elements would be missing at all kinds of levels. Your memorization strategy might be poor. It might not be secure enough. It might have taken you too long. I would often bring teachers pieces which I had memorized from scratch in one week, and could play correctly, and they would tell me I wasn't ready for the piece -- it would drive me nuts. But they were right.