13) Blackness in between instruments?
14) Balance between frequenzy ranges? (Bass - mid - treble)
I haven't seen Geoff respond, so in case he doesn't, I'll give you my own understanding of that.
13) This is kind of like the noise floor lowering. You hear a darker background, and since instruments cover that, you obviously don't hear the same effect where there is an instrument (in the sound picture). (I actually achieved an improvement of this very characteristic today, by moving one of my ART resonators a couple of feet).
14) I believe this would have to refer to coherence, specifically, the equality (of volume) between the 3 segments of the frequency range. Sometimes a speaker might be too bassy, for example.