Improvisations on Multi-Level Progressions

Rhythm Changes Grammar and Generated Equivalent Chord Progressions

This Rhythm Changes phrase structure grammar [1] was constructed based on the analysis of the sub-corpus of Rhythm Changes from Charlie Parker’s Omnibook [2,3] with a professional jazz musician.

(i) Rhythm Changes —> A1 + A2 + B + A
(ii) A1 —> τI + τ + σ + τ
(iii) A2 —> τI + τ + σ + ω
(iv) A —> A1, A2
(v) B —> δIII + δVI + δII + δV
τI, τ, σ, ω, δIII, δVI, δII, δV contents are learnt on the corpus.

This grammar has then been validated with jazz musicians.
The list of examples of equivalent chord progressions for Rhythm Changes generated with this grammar can be found here : Generated Equivalent Chord Progressions
This grammar enables us to generate multi-level progressions, ie. an analysis of a music progression upon several hierarchical levels. In our case, we have 3 different levels : the chord progression, the functional progression, and the sectional progression.

Generated Improvisations

In order to test the benefits of using multi-level progressions, we have generated improvisations using two music generation methods :

  • A base generation model taking only the chord progression level of the multi-level progression into account. (a simplified version of ImproteK [4])
  • Our extended generation model using all the information from the multi-level progression (ie. the chord progression, the functional progression and the sectional progression).

Example 1 – Improvisation on Thriving from a Riff

Data :
  • Chord progression generated by the grammar :
I II-   V7 I II-   V7
I7 IV7 III-   VI7 II-   V7
I II-   V7 III-   VI7 II-   V7
V-   I7 IV   #IVo I I
III7 III7 VI7 VI7
VI- II7 II- V7
I II-   V7 I   VI7 II-   V7
I   I7 IV   #IVo I II-   V7
Improvisations :
  • Base generation model :
  • Extended generation model :

 

Example 2 – Improvisation on An Oscar For Treadwell

Data :
  • Chord progression generated by the grammar :
I II-   V7 III-   VI7 II-   V7
V-   I7 IV7   IV- I   VI7 II-   V7
I   VI- II-   V7 I  VI7 II-   V7
I7 IV   bVII7 II-   V7 I
VII- III7 III- VI7
VI- II7 II- V7
I   VI7 II-   V7 III-   VI7 II-   V7
I   I7 IV7   IV- I I
Improvisations :
  • Base generation model :
  • Extended generation model :

Example 3 – Improvisation on Anthropology

Data :
  • Chord progression generated by the grammar :
I   VI7 II-   V7 I II-   V7
I   I7 IV   #IVo III-   VI7 II-   V7
I II-   V7 I II-   V7
V-   I7 IV   #IVo I I
III7 III7 VI7 VI7
II7 II7 II- V7
I   VI7 II-   V7 I   VI7 II-   V7
V-   I7 IV7   IV- I II-   V7
Improvisation :
  • Extended generation model :


No improvisation could be generated with the base generation model since no diminished chord appeared in the memory

References

[1] N. Chomsky, Studies on semantics in generative grammar. Walter de Gruyter, 1996, vol. 107.
[2] C. Parker and J. Aebersold, Charlie Parker Omnibook. Alfred Music Publishing, 1978.
[3] K. Déguernel, E. Vincent, and G. Assayag, « Using multidimensional sequences for improvisation in the OMax paradigm », in Proceedings of the 13th Sound and Music Computing Conference, 2016, pp. 117–122.
[4] J. Nika, M. Chemillier, and G. Assayag, « ImproteK : introducing scenarios into human-computer music improvisation », ACM Computers in Entertainment, vol.4, no.2, 2017.