Class: JazzModel::Chord

Inherits:
Base
  • Object
show all
Includes:
KeyContext
Defined in:
lib/jazz_model/chord.rb

Overview

A chord object represents a chord defined as an unordered collection of tones (non-octaval). Mixes in the KeyContext module to provide optional key context on the chord.

Creating a Chord

Chords should be created by indexing the Chord class like an array, like so:

Chord[symbol]

An alternative method of resolving a chord is to use the resolve method, though this is likely to become deprecated in the future when chord progression support/representation is added:

Chord.resolve(symbol)

This resolves a specified chord symbol into a new chord object using data regarding chord symbol-to-chord relationships. symbol can be any standard jazz chord symbol representable as plain ASCII (unicode support for other symbols such as full-diminished circle in the works). Can be prefixed with a key.

Object Relationships

A chord object has the following associations, exposed by methods:

  • symbols - Associated chord symbols.

  • primary_symbol - Primary chord symbol.

  • chord_scales - Chord-scale relationship objects. See ChordScale.

  • modes - Direct access to associated scale modes through chord_scales.

  • tones - Sequence of tones associated with the chord. See ToneSequence.

  • voicings - Voicings associated with this chord.#

Example Usage

Creating Chords Without Key Context

Chord['maj']
Chord['min7'
Chord['maj7#11']
Chord['7#9']

Creating Chords With Key Context

Chord['C7']
Chord['Bbalt']
Chord['Gbmaj7']

Getting Chord Notes

Use notes to retrieve a collection of notes, which actually delegates to tones.notes:

Chord['C7'].notes
# => ['C', 'E', 'G', 'Bb']

Chord['Cmaj7#11'].notes
# => ["C", "E", "G", "B", "F#"]

Correctly Interpets Theoretical Keys (not just pitches)

Note the #11 is correctly interpreted as E# and not enharmonic F here:

Chord['Bmaj7#11'].notes
# => ["B", "D#", "F#", "A#", "E#"]

Also correctly interpet tones off of enharmonic base keys:

Chord['Gbmaj7'].notes
# => ["Gb", "Bb", "Db", "F"]
Chord['F#maj7'].notes
# => ["F#", "A#", "C#", "E#"]

See Related Scales

Chord['min7'].modes.names  # .names == .map(&:name)
# => ['Dorian']
Chord['min7'].modes[0].scale.name
# => "Major"

Chord['Amin7'].modes.names
# => ['A Dorian']

Class Method Summary collapse

Instance Method Summary collapse

Methods included from KeyContext

included

Methods inherited from Base

load_definitions

Class Method Details

.resolve(symbol) ⇒ Object Also known as: []

Resolves a chord symbol into a chord. Implementation is somewhat flakey due to the potential ambiguities arising from specifying key and symbols together.



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# File 'lib/jazz_model/chord.rb', line 107

def resolve(symbol)
  in_key = nil

  return nil if symbol.nil?
  symbol = symbol.dup

  Key.all.each do |k|
    if symbol.starts_with?(k.name)
      in_key = k
      symbol.sub!(k.name, '').strip
      break
    end
  end

  chord_symbol = ChordSymbol[symbol]

  # Perhaps the matched key was really part of the name of the chord, try that:
  if chord_symbol.nil? && !in_key.nil?
    symbol = in_key.name + symbol
    chord_symbol = ChordSymbol[symbol]
  end

  # If still not found, must be invalid:
  return nil if chord_symbol.nil?

  chord = chord_symbol.chord
  chord.key = in_key unless in_key.nil?
  chord
end

Instance Method Details

#symbols_list ⇒ Object 



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# File 'lib/jazz_model/chord.rb', line 98

def symbols_list
  self.symbols.map {|s| s.name }.join(', ')
end