By being "right on the quarter note," I mean keeping a STRONG internal pulse and/or foot-tapping of beats 2 and 4, and playing your walking bass line to the T. Perfectly on nearly every note. Rather than using "1 2 3 4" as a reference point, use "_2_4" (_ representing beats 1 and 3 not tapped). Then the next step is doing this so much that you're almost early.
Then there's the whole piano comping thing in jazz where the chords should represent triplets and be on with the snare drum, yadda yadda...
No tutorials on YouTube ever mention these things, yet it's like the most important part! Distinguishes a professional from an amateur, to be totally honest. God, I really should start a music channel on YouTube talking about this stuff... feels like no one outside of my small circle of people knows this.
