What's a minor key? Ok, well, I know how key signatures work, I think. I know that when you're in say, the key of C, all of the possible chords are made up of the notes in a C scale, like Cmaj, Amin, Fmaj, etc. And I know that each major chord has a relative minor, so in this case, that would be Amin. So, how does the key of Cmaj differ from Amin? Wouldn't they have the same notes in them?