scale_finder

This is the module to recognize chords and scales and perform correct transpose to another scale.

npm install scale_finder --save

Chord parsing

To recognize a chord just send it to function "parse_chord".

Example 1:

var sf = require('scale_finder');
var chord = "Am/G"
var chord_object = sf.parse_chord(chord);
console.log(chord_object):
{ 
    root_tone: 9,
    bass_tone: 7,
    root_key: 'A',
    bass_key: 'G',
    tones: [ 0, 3, 7, 10 ],
    keys: [ 'A', 'C', 'E', 'G' ],
    suffix: 'm' 
}

Chord object contains:

root_tone - absolute root tone value according to tones table.
bass_tone - if bass tone exists contains absolute bass tone according tones table or null if not exists
root_key - letter of root tone, because it is possible to have same tone but different letters (ex: A# and Gb)
bass_key - letter of bass tone
tones - chord_tones - array of tones in chord relative to root tone which is 0
keys - chord_keys - array of letters for chord tones 
suffix - chord modifier

Find scale

To find scale put array of chords to the "find_scale" function:

Example 2 - Straight D major:

var sf = require('scale_finder');
var chords = [ 'D', 'A', 'Bm', 'G' ];
var scale_object = sf.find_scale(chords);
console.log(scale_object);
{ 
    root_key: 'D',
    scale: 0,
    tones: [ 0, 2, 4, 5, 7, 9, 11 ],
    keys: [ 'D', 'E', 'F#', 'G', 'A', 'B', 'C#' ],
    extra_tones: [],
    extra_keys: [],
    extra_steps: [] 
}

Example 3 - G major with out of scale Eb and F chords.

var sf = require('scale_finder');
var chords = [ 'G', 'C', 'Em', 'D', 'C', 'G', 'Am', 'Hm', 'Eb', 'F' ];
var scale_object = sf.find_scale(chords);
console.log(scale_object);
{ 
    root_key: 'G',
    scale: 0,
    tones: [ 0, 2, 4, 5, 7, 9, 11 ],
    keys: [ 'G', 'A', 'B', 'C', 'D', 'E', 'F#' ],
    extra_tones: [ 3, 8, 10 ],
    extra_keys: [ 'Bb', 'Eb', 'F' ],
    extra_steps: [ 3, 6, 0 ] 
}

Transpose

To transpose chords sequence to another key, put chords array and new root key to "transpose" function. Transpose function returns transpose map:

Example 4 - Straight A minor to B minor:

var sf = require('scale_finder');
var chords = [ 'Am', 'F', 'C', 'G' ];
var scale_object = sf.transpose(chords, "B");
console.log(scale_object);
{ 
    Am: 'Bm', 
    F: 'G', 
    C: 'D', 
    G: 'A' 
}

Example 5 - G major with out of scale Eb and F chords to C, C# and Db scales:

var sf = require('scale_finder');
var chords = [ 'G', 'C', 'Em', 'D', 'C', 'G', 'Am', 'Hm', 'Eb', 'F' ];
sf.transpose(chords, "Db");
{ G: 'Db',
  C: 'Gb',
  Em: 'Bbm',
  D: 'Ab',
  Am: 'Ebm',
  Hm: 'Fm',
  Eb: 'Bbb',
  F: 'Cb' }

sf.transpose(chords, "C#");
{ G: 'C#',
  C: 'F#',
  Em: 'A#m',
  D: 'G#',
  Am: 'D#m',
  Hm: 'E#m',
  Eb: 'A',
  F: 'B' }
  
sf.transpose(chords, "C");
{ G: 'C',
  C: 'F',
  Em: 'Am',
  D: 'G',
  Am: 'Dm',
  Hm: 'Em',
  Eb: 'Ab',
  F: 'Bb' }