Some lesser explored territory for me here: harmonic minor.
I've never verified it, but my impression from music classes was that harmonic minor is more popular than natural minor, but I've always been more drawn to natural minor in my own writing.
Harmonic minor has a leading tone - the 7th note of the scale is a half step below the tonic, whereas natural minor has a subtonic - the 7th note is a whole step below the tonic.
I think the reasoning is supposed to go that in western music, we're more drawn to leading tones, those notes that practically force a resolution in order to satisfy. But if you drop it just a half step further, then that primal drive for resolution is nowhere near as strong.
Apparently, I'm just not as big into resolutions as that, which may explain why I seem to be forever drawn to flat 7s in a major scale.
And I've just learned that apparently my beloved flat 7 is part of mixolydian mode.
The more you know.