The geometry of music revealed! The red lines connect notes that are a major third apart. The green lines connect notes that are a minor third apart. The blue lines connect notes that are a perfect fifth apart.
Each triangle is a chord with three notes, called a triad. These are the most basic chords in Western music. There are two kinds:
A major triad sounds happy. The major triads are the triangles whose edges go red-green-blue as you go around clockwise.
A minor triad sounds sad. The minor triads are the triangles whose edges go green-red-blue as you go around clockwise.
This pattern is called a tone net, and this one was created by David W. Bulger. There’s a lot more to say about it, and you can read more in this Wikipedia article:
and this great post by Richard Green:
The symmetry group of this tone net is important in music theory, and if you read these you’ll know why!