The whole concept of modal music is that there is no "chords"
When u pick up "so what" and see bar upon bar dmin7, its wrong, and its not what miles intended. It should be bar upon bar of "D dorian", not Dmin 7
The concept of modal music is to create sounds and tensions out of the one scale, without the "vertical" harmonic rules of most other forms of contemporary music.
When i say vertical, im referring to the systematic vertical(on a cleff) stacking of chords: 1, 3, 5, 7, 9, 11, 13
There is no 9, 11, or 13, in modal music. They should be refered to as 2, 4 and 6 due to the fact that modal music should be appproached horizontally, and not in the traditional "upper structure" sense
So when a pianist(a good one) comps over So What, they're not playing Dmin 7, they are actually clustering groups of 4ths and 3rds from within the dorian mode to create sounds and colours of their own choice.
like: E A D G C - D G C E A - F A D G C - B E A D G etc etc
So in other words, you dont need a "chord" for dorian to be dorian. Dorian is what it is - Dorian - Its not just a scale. Its a tonality