> in music Music uses both systems. A chromatic approach uses a 0-indexed system while the classical diatonic scales and intervals are indexed at 1. A perfec

> in music Music uses both systems. A chromatic approach uses a 0-indexed system while the classical diatonic scales and intervals are indexed at 1. A perfect 5th is a chromatic interval of 7 semitones. 1-do(0) 2-re(2) 3-me(4) 4-fa(5) 5-sol(7) 6-la(9) 7-ti(11) The question is whether it's more useful to count the notes that appear and label them with numbers, or to measure the difference between them.