Today's Blogging A-to-Z challenge entry goes back in time a little bit. Before there were keys, there were modes: the original scales used in Ancient Greece that still pertain today.
Our C-major scale roughly corresponds with the Ionian mode. (I say "roughly" because while the fifth, octave, and probably fourth notes would have sounded the same back then as they do now, the rest of them probably would have sounded slightly out of tune to modern ears. This is a topic for next week.)
If you start on D, you get the Dorian mode:
It's not quite D minor, because instead of a flat 6th and natural 7th as in a minor key, we have a natural 6th and flat 7th. You can hear Dorian mode in Deep Purple's "Smoke on the Water."
Next comes Phrygian mode, starting on E:
If you start on F, you get Lydian; G, Mixolydian; A, Aeolian (corresponding closely to natural minor); and B, Locrian.
I mentioned Deep Purple because everything old is new again. A lot of modern popular music has reached back to modes, mainly (I think) because they sound cool. Lydian mode has a tritone instead of a perfect 4th; Locrian just sounds...off.
In fact, while Ionian, Dorian, Phrygian, and Aeolian pop up a lot, there aren't many examples of the others. But they're out there.
Homework assignment: Find modal pop songs (LMGTFY). Then listen to them.