What is a negative harmony?
I've just stumbled upon this video and was quite puzzled by it. At first I thought it would be the tune simply reversed, that is, like what you get when you play it back in reverse. But quite soon I realized that it was not the case - the tune goes exactly in the same direction as in the original song. Then what is it? Is it just changing minor chords to major and major to minor or is it some deeper and more intricate modification?
The idea is to apply the idea of melodic inversion to harmony (or so I get.) One can take a melody and invert the melody about an axis (see Die Kunst der Fugue). For example, the melody C,E,G,Ab,G could be inverted about C to give C,A,F,E,F (using tonal inversion or) C,Ab,F,E,F (real inversions). I borrowed the terms from fugue theory where tonal answers go by letter names and real answers go by half-steps (I think.) Harmonies are derived by taking chords and inverting them about the melody note (or maybe the root or bass?). The proponents give these chords funny names that I don't remember. Minor chords become major though; perfect intervals stay perfect.
In earlier music, one could also invert about another axis. C,E,G,Ab,G could be inverted about the note D giving E,C,A,G#,A.
