The whole of music, both in a technical and emotional sense is totally dependent on relationships. When I think about any of my favorite artists, They all have deep relationships within the band. When you hear a Motown track you hear and feel the deep relationship among the Funk brothers.
Steely Dan, which changes musicians the way most people change their clothes, always hires musicians that have some sort of connection with one another. You can always tell when musicians have a relationship; the sound is warmer and the groove is undeniable.
Drummer Sly Dunbar and bassist Robbie Shakespeare are the rhythm section in Reggae. When they work with other artists outside of Reggae they immediately bring the music to a higher level. This is also true of the Wrecking Crew, Booker T and the MG's, The Muscle Shoals Rhythm section and many others.
Musical relationships are much more difficult in today's fractured enviornment with remote session playing, synthesizers and such. It is also the reason why so many recordings sound artificial. There is simply no relating going on.
Too many musicians say "I hear you" when they really don't and that's the problem. Listening to your fellow players is step one, connecting with them is step two. I and many others have played gigs where the notes were right and the feel was all wrong.
A recording date is a good example. Most good musicians will have the notes within several takes. The thing that drives the number of takes higher is getting a feel, getting the music to settle into a pocket. This is where "hearing" each other is the difference between a successful or mediocore recording.
The formula is simple: Listening+hearing+connecting= good music.
The groove continues...