ChordsDescriptors

streaming mode | Tonal category

Inputs

  • chords (string) - the chord progression
  • key (string) - the key of the whole song, from A to G
  • scale (string) - the scale of the whole song (major or minor)

Outputs

  • chordsHistogram (vector_real) - the normalized histogram of chords
  • chordsNumberRate (real) - the ratio of different chords from the total number of chords in the progression
  • chordsChangesRate (real) - the rate at which chords change in the progression
  • chordsKey (string) - the key of the progression, taken as the most frequent chord
  • chordsScale (string) - the scale of the progression, whether major or minor

Description

Given a chord progression this algorithm describes it by means of key, scale, histogram, and rate of change. Note:

  • chordsHistogram indexes follow the circle of fifths order, while being shifted to the input key and scale
  • key and scale are taken from the most frequent chord. In the case where multiple chords are equally frequent, the chord is hierarchically chosen from the circle of fifths.
  • valid chords are C, Em, G, Bm, D, F#m, A, C#m, E, G#m, B, D#m, F#, A#m, C#, Fm, G#, Cm, D#, Gm, A#, Dm, F, Am. Chords that not follow this terminology (i.e. Gb) will raise an exception.

Input chords vector may not be empty, otherwise an exception is thrown.

References:

[1] Chord progression - Wikipedia, the free encyclopedia, http://en.wikipedia.org/wiki/Chord_progression

[2] Circle of fifths - Wikipedia, the free encyclopedia, http://en.wikipedia.org/wiki/Circle_of_fifths

Streaming algorithms

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