the approximation of the 12 pitches of western music by modulus-12 math, forming the circle of halfsteps, means that musical intervals can also be thought of as angles in a polar coordinate system, stacking of identical intervals as functions of harmonic motion, and transposition as rotation around an axis. thus, in the multiplication example above from hanson, "p@m" or "p/m" ("perfect 5th at major 3rd", e.g.: { c e g b }) also means "perfect fifth, superimposed upon perfect fifth rotated 1/3 of the circumference of the circle of halfsteps". a conversion table of intervals to angular measure (taken as negative numbers for clockwise rotation) follows: