Memorizing is necessary for learning a piece quickly and well, playing musically, acquiring difficult technique, performing flawlessly, eliminating nervousness, etc. To memorize piano music, simply use the rules for learning, with the added proviso that you memorize everything before you start to practice the piece. It is the repetition during practice, from memory, that automatically implants the memory with little or no additional effort compared to the effort needed to learn the piece. The first important step is HS memorization. When you memorize something beyond a certain point, you will almost never forget it. Use the same procedures for memory maintenance. For memorizing, you can use music memory, hand memory, photographic memory, keyboard memory/mental play, and music theory. The human memory function is associative and a good memorizer is good at finding associations and organizing them into an "understanding" of the subject matter. A super memorizer is an expert in the development and use of efficient algorithms for memory. Music is one of the most efficient algorithms for memory; perfect pitch will also help. All these memory methods should culminate in MP -- you can play the music, and hear it, as if you have a piano in your head. MP is essential for practically anything you do at the piano and it enables you to practice memorizing at any time. We saw that good memorizers are good because their brains are always memorizing something automatically; you can train your brain to do this only if you can do MP. You should have two repertoires: memorized, and sight reading. MP brings with it a whole new world of musical capabilities such as playing a piece from anywhere in the middle, perfect pitch, composing, performing without flubs, etc., which we had mistakenly attributed to "talent". Many of those miraculous feats that the musical geniuses are fabled to have performed are within reach of all of us!