README.md

interval-coords

This module makes it possible to convert music intervals in so-called "simple format", into a coordinate in the format [steps, semitones], which represents how many diatonic steps and semitones there are between two tones, respectively.

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].

An augmented fourth, A4, is represented by [3, 6], while a diminished fifth is [4, 6]. The second number is the same, which tells us that they have the same sounding pitch.

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 -> [7, 12]
icoords('m13')  // minor 13th -> [12, 20]

// You can also use "negative" intervals (going down)
icoords('m-2')  // downwards minor second -> [-1, -1]

icoords(simpleInterval) -> [steps, semitones]

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.