Another interesting feature about this endlessly repeating four-chord progression: This song has an ambiguous tonality. “Teenage Dream” denied the listeners the I chord to create weightlessness; in “Get Lucky,” it is aurally unclear what the I chord even is!
See, the song can be heard in two different keys. Most of the time it sounds as if it’s in the minor mode of A Aeolian*—the scale goes A B C D E F G—essentially, a form of A minor, which appears as the third of the four chords (“We’re up all night for good fun”).
But the first chord of the progression isn’t A minor, it’s D minor. The song slides smoothly back to it each time (“I’m up all night to get some”). The insistence of the D minor creates the aural illusion that the song could in fact be in the minor mode of D Dorian—D E F G A B C. Note that the D Dorian scale contains all the same notes as A Aeolian, all the same keys on the piano. The only difference is what key you start on.
