There's a maneuver at the piano keyboard where you reach up to a higher note, let's say with the ring finger of the right hand, and then while still holding down the note, sliding up one of the other fingers, let's say the second finger, without lifting the ring finger until the note is safely held by the second.  It's a move that let's you smoothly make your way up the keyboard, in a melodic line; or jump around safely in some gymnastic arpeggios. 

But when I play certain composers, that finger slide just feels wrong.   Not that it's bad (it is bad, very bad.  It is a louche and decadent position).  I just feel that the  music demands a carefully discovered hand position...once you've got that position, playing the music is easy, it slides in to place, just occurs.  Messiaen scores are formidable, but I really do think that the strength of his compositional craft was the capacity to throw his hands on the keyboad, remember exactly what had happened, and notate it  so accurately that someone else could throw their hands upon a second piano to acheive the same result.  The notation is not  to capture the specific notes...the notes are the epi-phenomenon of a physical gesture.  Recreate that principle twitch, and the notes fill themselves in. 

This is a bit of a crank position.  But I also remember the years I spent studying from the Alfred Cortot Rational Principles of Pianoforte Technique .

    

Cortot writes

"In the beginning of this work, we stated that we thought it possible to group all the problem of pinaistic execution into five essential categories.  We conceive this classification in the following manner:

1. Equality, independence and mobility of fingers
2. Passing under of the thumb (scales - arpeggios)
3. Double notes and polyphonic playing
4. Extensions
5. Wrist technique, execution of chords

We consider that in the whole literature of the pianoforte, no difficulty exists which cannot be placed under one of the preceding headings."

Throughout the text, I get the sense that Cortot also looks for the root cause, the underlying gesture that explains each passage.  The whole series of exercises are designed to be played through each morning, like calisthenics.  Time to practice, if I'm going to play Raw Moon with any conviction.