| - indicating minor, perhaps?
Clearly, Berklee students are bonkers.
If you consider the relative minor of a scale, the third is a fourth below the sixth (that doesn't sound silly at all...) so in a minor context it could be seen as the 'relative dominant of the minor' or something silly like that. Of course, the tritone of the dominant, being between two elementary chord tones, is a lot more obvious than the tritone of the third, between the fifth (which is often not played but implied) and the ninth (which is not always played or even implied), but I'm really just speculating based on why I'd see a III- as a dominant.
Jeff |