If I sing a major third on the root it becomes a major seventh when I go to the IV If I sing a flat seventh it resolves to a major third when I go to the IV Thirds and sevenths

Their relationship is unstable It’s even been called the devil’s interval But together they’re part of functional harmony The seventh of V goes down to the three

Of the root and we’re back to the third which becomes major seventh when I go to the IV And then I’m back to flat seven resolving to the major third when I go to the IV Thirds and sevenths

The third of the V becomes major seventh of the root The third of the V becomes a major seventh of the root Then it’s the tritone of the IV The unstable tritone of the IV and then we are

Back to the major third which is a major seven when I go to the IV And the dominant seven points down to the major third when I go to the IV Thirds and sevenths Talking about thirds and sevenths All the music theory nerds are in heaven When we talk about thirds and sevenths