Negative harmony
A relatively new area of music theory that still sparks debate amongst theorists, negative harmony stems from the core idea of polarity, in that, just like an audio waveform, the notes in a melody or the chords in a progression can be either positive or negative. Negative harmony involves flipping notes or chords around an axis, so their states become inverted, and you end up with a mirror image of the notes you started with – eg, major chords become minor chords, and so on.
Every piece of music has a key centre (or tonic note) that all notes and chords within the piece want to pull
