I know what you mean about memorising tunes. Apart from exam pieces I've never practised anything thoroughly enough to truly internalise the score. Recently I joined a male voice choir that sings from memory. Endless repetition appears to be the main strategy and it certainly works. Also I think you approach a piece differently if you know that you've got to do it without the score. If all else fails there's often a simpler version.......
Fascinating work. I love the way Paul Desmond uses the opening phrase on a very early ('52?)
version of 'Stardust'. Think he precedes it with a touch of 'little man you've had a busy day'.
What a star!