Over the years, I have refined my approach to learning new pieces more efficiently. Below I share some tips.
RULES FOR LEARNING NEW PIECE
start memorizing a new piece at the beginning of your learning process
do not stick your eyes on the score! instead, spend more time watching your hand, finger, and feel your body movements.
break it down: memorize only RH, LH separate, or even just 1 voice at a time.
read a small phrase from the score without playing it, read it till it is committed it to memory. Now try playing it without looking at the score. Repeat this small phrase a few times. Then move on
start not necessarily from the beginning of the piece, but with the most difficult passage first
learn similar sections together - e.g. learn exposition and recap side by side, and note any subtle differences
As soon as you feel your brain is tired from memorizing new music, STOP! take a 10 min break. do some stretches. Or even just call it a day and rest!
How to Eliminate Memory Slips
How to Memorize Music 5 Times Faster
POWER OF VISUALIZATION
Check out this interesting study on the power of mental practise
It is critical for me to trial run a newly learnt piece at different pianos, in different environment. Originally I thought this is to simply build confidence, until I found an article that explains something called 'context-dependent memory'. In short, what you learnt is recalled best in the same physical environmental context where you learnt it. Read this article for more details.
The Left Hand looks so daunting to memorize!
Let's just look at the Left Hand notes
Look at groups of four
Now let’s remove every second note of each group of four
One can now easily see that this passage is just B minor scale. The note removed was just a chromatic auxiliary note!
To help with developing analytical memory, below are books that I find helpful. I didn't read all of them in great details. My goal was to get a general understanding of concepts in composition, analysis, and harmony, and be able to come up with some form of analysis that serve as aid in analyzing and memorizing music.
Top 3 recommendations
Salzer, Felix - Structural hearing : tonal coherence in music
Hindemith - The Craft of Musical Composition
Schoenberg - Theory of Harmony
Other helpful books
Rosen, Charles - Sonata Forms
Rosen, Charles - Beethovens Piano Sonata
Bernstein, Leonard - The Answered Question (Lecture Series)
Harris, Robert - What to listen for in Mozart
Gauldin, Robert - Harmonic Practice in Tonal Music
Piston, Walter - Harmony
Persichetti, Vincent - Twentieth-Century Harmony
Brindle, Reginald Smith - Musical Composition
Dallin, Leon - Techniques of twentieth century composition; a guide to the materials of modern music
Delone, Richard - Aspects of twentieth-century music
OTHER MEMORY AIDS
play the piece on your lap or table.
Mentally visualize and feel the motions of your entire body with closed eyes while simulating physical movements of playing the piano without actually touching a piano.
singing any melodic part - not just main melodic line, but also bass or middle voices in a chordal passage - do this for each voice separately
For complex rhythmic passages, make sound such as "dah dah dah" to rehearse the rhythm. At the same time tap your feet.
STRESS TEST YOUR MEMORY
After committing a piece into memory, try these from memory:
play a bar, or opening of a bar, then skip a bar or two
play a bar, then play the previous bar, or skip a few bars backward
pair up like passages from different spots within the piece - jump around back and forth - do this from memory (but make sure you know where you are at within the piece)
play left hand notes using your right hand, and vice versa
I will do these hands separately, or hands together. This technique allows me to have many starting points in a piece, such that if I lose concentration accidentally during a performance, I can re-start without pause .