"never be a slave to the stave"

Ah - all the 30s 'big bands' and many jazz bands then and now supply part music - you are EXPECTED to be able to play what the COMPOSER/ARRANGER set out...

Only 'soloists' are allowed the 'luxury' of 'making it up as they go along'...

viz...

QUOTE
because the are a Musician, they can obviously play music without practising endlessly
UNQUOTE

I call these 'artists' "B-graders" - no matter how good they THINK they are, they can never understand WHY they never seem to improve - of course that is being kind and assuming they can tell the difference...

The WHOLE POINT of the original development of various forms of music notation was to PRESERVE good music, intended to be an AID TO MEMORY, not some slavish imprisonment of 'artistic taste'... I personally love the guide in front of me (and as a pipe organ and choir/ensemble muso, I can read full 'conductor score' - with multiple simultaneous parts), as I can use that as a starting point. I love those 'fake books' with the tune and chord structure - I can start playing immediately (tunes I have NEVER heard before take a few minutes to get up to speed) without trying to remember millions of tunes...

Of course if someone can only 'play by ear', I still respect them (based on their output) - I just think it sad that they are unnecessarily limiting their potential capabilities...