The Math behind Piano Chords

Abstract

In this poster, I shall describe the mathematics behind piano chords. Both major and minor chords are formed by three keys or notes, and both follow the rule of 7. In a major chord, we follow a 4 + 3 rule, where we pick the root note, and then 4 keys higher and then 3 keys further up. In a minor chord, we follow a 3 + 4 rule, where we pick the root note, and then 3 keys higher and then 4 keys further up. Just a small change in the middle key results in a big change in the mood of the chord (happy vs scary or sad). There are several variations of these formulas when we have chords with inversions. I shall explore the math behind this mood change and explain other mathematical formulae behind piano chords.