The Minor Seventh
The farther we get from the center, the less consonant the notes are, when played against the tonic. Consonance is a whole subject. It’s generally spoken of as though it could be plotted on a scale, from consonance to dissonance. I think this is a big mistake. Consonance has more than one dimension. Trying to force these independent dimensions of consonance onto a one-dimensional scale leads to unnecessary confusion.
Anywayy … The minor seventh is a pretty dissonant note in all dimensions. It’s three moves away from the tonic, down a third and up two fifths:
The ratio is 9/5.
This is some beautiful, exotic harmony.
Here’s a progression that shows off the flavor of the b7, in just intonation:
Hey, that’s beautiful! I worked it out as an illustration, with the idea of showcasing the minor seventh, and it turned out to be really nice music.
See why I’m in love with the lattice? It’s a beauty engine.
Next: Untempered Vs. Tempered