The major key universe

It's more than the diatonic major scale

Minor keys are complicated, because there are so many different minor scales. Major keys seem simpler, because there is only the one major scale. At least, that is how things worked in Western Europe between 1700 and 1900. In present-day Anglo-American pop, though, we need to expand our idea of what a major key is.

It's very common for major-key songs to use notes and chords from outside the major scale. The most common of these is the flatted seventh scale degree and the corresponding bVII chord. These are omnipresent features of any music descended from the blues.