This is my first post on this forum. If you play by ear only without any theory and you cannot and never could read music. Does that put you in a different category? Erroll Garner was one of those people. Never knew Art Tatum was though, if so, it makes him even more a rare talent.
I have played for 70 years without being able to read a score or anything. I play jazz. It's an ability to understand which notes make what sound. Practice for years and years is to me the biggest improver of style. Your subconscious brain does the rest. Fingering technique is the hardest part and where scale practice is vital.
The piano keys all have the sounds there it's just a matter of knowing what keys will give a particular sound. A bit like a singer forms the sound from the brain sound recall.
This is another form of playing by ear, totally.
Alan
I (who own over 200 individual Tatum performances) did not know this until the other day, when I was perusing a possible new textbook for my Jazz History class. Evidently he learned to play from rolls, being ALWAYS almost completly blind. Guess that "he studied Chopin Etudes before his eye was put out in a teenage fistfight" stuff is spurious misinformation, planted by the legitos...
You are right Alan, the subconcious brain should do the work after all the practice, but there is a difference between Jazz and other improvised genres and Classical or arranged or recreative genres. The classical pianist has to play all the notes as they are written, because s/he is recreating what a composer wrote. It's harder to let your subconcious go when you are doing that; improvising IS the subconcious, revealed immediately for all to hear, regardless of what genre or style or vehicle. The challege the improviser faces is to have his subconcious come out organized, not as random spewage (although that can work in a pinch

, and much classical music is little more than that.).
And so we are all after the same thing, just approaching it from opposite ends of the spectrum. The classical player builds the structure from blueprints, with the goal of having it sound fresh, as if it had just been written. The improviser (Jazz, Raga, anything) builds on the spur of the moment, and must convince his listeners that the structure s/he has built is valid, not a rambling mess.

Yes, we are in different categories, but we are all doing the same thing.......