interval-coords

This module makes it possible to convert music intervals in so-called "simple format", into a coordinate in the format [octaves, fifth], which represents how many octaves and fifths you need to "jump" before arriving at the interval.

For example P1 means "perfect unison", and so the coordinate would be [0, 0] because there's no movement.

Another example, M3 means "major third" and the coordinate is [-2, 4]. This means that in order to travel a "major third" up, you first go 2 octaves down, and then 4 fifths up

This way of representing intervals and notes is a powerful one, and it lets us take advantage of numeric computations instead of string-parsing and long if/else statements

usage

var icoords = require('interval-coords');
 
icoords('P1')   // perfect unison -> [0, 0]
icoords('M3')   // major third -> [-2, 4]
icoords('P8')   // perfect octave -> [1, 0]
icoords('m13')  // minor 13th -> [4, -4]
 
// You can also use "negative" intervals (going down)
icoords('m-2')  // downwards minor second -> [-3, 5]

icoords(simpleInterval) -> [octaves, fifths]

Given a string with a "simple format" interval, it returns the corresponding coordinate vector of that interval.

"simple format" interval

A simple interval is a string in the following format:

dd, d, m, P, M, A, AA followed by an optional - sign (for negative intervals), followed by the number of the interval.

Not all combinations are valid, e.g. P3 (a "perfect third") doesn't make sense, but P4 ("perfect fourth") does.