Keith Emerson is known as someone that still took lessons, despite already being successful. He continued his studies.
Invested in his art, if you will.
Classical training and practice doesn’t necessarily mean one has to play complex music.
Playing slowly and accurately can be harder than playing fast.
When your heart rate is going faster than the music, you have to do division really, whether it’s conscious or not.
Music theory training and practice teaches one how to count beats and more importantly often, rests.
It teaches what notes can fit into what scale, inversions, correct fingering techniques and all sorts of base level info that many artists don’t have to draw upon.
While not knowing theory can create a style, it is more often a limiting factor.
There are many records out there that feature one or two good songs, but after you listen to the whole album, you realize that the performer only knew how to play in one or two keys, did similar chord progressions, solos, etc.
Things can get old very fast, as many one hit wonders have found out.
Worse, an artist not having the resources of a good education, may feel like they’re in a rut or that they can’t play certain types of pieces or what’s in their head.
It’s like trying to command speech, when you only know a few words.
You lose the audience quickly, even though you may have made an excellent introduction.
Wendy is the queen of nuance and note attack.
You can hear that she put a great deal of time into how the notes of SOB spoke and interacted.
This kind of deep understanding of music is commonly overlooked.
It illustrates an ability for arrangement and harmony that few can possess when working in a layered and synced mono voice mode.
One has to hear where a piece is supposed to go, long before the notes are played.
Harmonic and contrapunctual lines that support a melody may have to be layed down beforehand, where it’s not as easy because you can’t “hear” where things are going.
The performer may have to count and not have anything to guide them.
Harder than it seems and no easier if the music is slow or with few counterpoint lines.
Try playing a simple straight 4 or even I, IV, V progression very slowly over the length of a whole song without a metronome, on say, a bass instrument.
Note attacks have to be considered more at that tempo, so having music theory practice and training is valuable.
Notation, sight singing and other aspects of classical training can make an artist more efficient also.
Knowledge is better than ignorance.
It provides choice.