Trained or ear
If any of my comments appear to insult anyone .. Tuff!!..(Just kidding).
My intentions would be more of a challenge to expand your musical knowledge.
I believe it would be foolish to not study theory, music structure, score reading,
and understanding charts.
This along with practice to increase your playing skills, is the foundation
to be the best you can be.
The next natural step after a learned foundation, is to develop your ear..
This will give you the freedom that will enable you to be comfortable as a performer.
Your ear will allow you to ab-lib with the tune. But it is essential that you have the foundation
to do it right.
There is a learning progression, and it is pretty much the way I have stated.
Here are some real experiences that I have found to be true..
My training years were classical study on accordion.. this developed my so called "chops".
I moved on to theory, also voicing of chords , alternate chords, dropped 2's, bi-tonal..
You get the idea,,, This is the stuff that will make you better as you mature as a player..
(my last statement is what is usually lacking with classical trained pianist).
If you can not read scores or charts, professionally you are done.. If you have any
interest in larger bands with elaborate arrangements, or a studio musician .. forget it.
Most untrained folks get use to a 1.4.5 chord progression..
It sounds great to your family played with an arranger, but is really so empty..
You are short changing yourself. Study theory some more.. understand chord structure.
And practice voicing of chords on your right hand and left hand too. Learn to play the chords
in piano mode on your arranger, using expanded chords and substitute chords. It is in you,
you just have to do it.
Being locked into music in front of you... it is a crutch. Other than a specific arrangement with 18
players in a band.
You already know your material, you just don't know you do.
Early 80's (before I used SMF;s or arrangers), I relied on my music books.
Songs I performed a zillion times.
One day while working with a young lady (of course).. I forgot my music .. we were playing
at one of our regular jobs..
Guess what we didn't miss a beat, (I think it helped that my girl was "hot").
From that day on I didn't need the books.. New songs I would learn at home.
(maybe take an index card with chords).
I hope I have said something to challenge you , or at least have a better understanding.
Both a trained mind and a "good" ear together is the ultimate... You still need to practice.