chemart / music-ac

hub:
  repo_type: generator
  builtin: music-ac
  tags:
  - banzhaf-yamamoto
chemistries:
- id: music-ac
  name: Algorithmic chemistry for music composition
  intuition: 'Composition without a fitness function. A molecule is a stack of lines of musical elements
    with a displacement, so notes, chords and harmonic functions can sit in registered columns. Recombination
    rules join fragments that fit stylistically - a melody grows only by steps to a neighbouring note,
    a bar only takes a chord that contains its first note, and bars are only joined along cadence rules
    - and a phrase is finished when it is cut out and capped with Start and Stop, after which no rule
    matches it unless it still carries an avoid note. The style is in the rule set rather than in an evaluation
    step, so every product is well formed by construction.

    '
  aliases:
  - Miura-Tominaga music chemistry
  - algorithmic music composition with an artificial chemistry
  origin: Miura & Tominaga, 2006 (homophonic); Tominaga & Setomoto, 2008 (polyphonic)
  book: '16.4'
  refs:
  - '[592]'
  - '[854]'
  - doi:10.1007/978-3-540-78761-7_49
  family: application
  kind: generator
  constructive: true
  S:
    repr: 'objects (molecules) are stacks of lines of elements written disp#elements/ per line, the displacement
      counting columns relative to the first line: 0#C4D4E4/ is a melody fragment, 0#C4D4E4F4G4A4B4C5/0#TCCCCCCC/
      one bar under the tonic chord C, and 0#Start...Stop/1#T.../ a finished four-bar phrase. The species
      id is this canonical notation; the structure is the music the object carries (notes, chords and
      functions)

      '
    definition: implicit
    notes: '25 element kinds: the notes C4, D4, E4, F4, G4, A4, B4, C5 (eighth notes of the C major diatonic
      scale in one octave), the triads C, Dm, Em, F, G, Am and Bm (the paper''s Bm-diminished, written
      without the degree sign), the chord functions T (tonic), S (subdominant), D (dominant) and D2 (second
      dominant), and the control elements Degree, Chord, Avoid, Start, Stop and Dummy. The paper counts
      24 kinds and lists exactly those without Dummy, which its own initial objects use.

      '
  R:
    definition: implicit
    arity:
    - 1
    - 2
    scheme: 'recombination rules lhs -> rhs over patterns, where <1> matches one element, <*1> (left end
      of a line) and <1*> (right end) match a sequence of zero or more elements and <1..7> abbreviates
      <1><2>...<7>. The objects matched by the left-hand patterns are consumed and the right-hand patterns,
      filled with the matched elements, are produced; each wildcard occurs once on each side, so elements
      are conserved. The 65 rules implement the five steps of the algorithm: (1) 0#<*1>D4/ + 0#Degree/0#D4<2>/
      -> 0#<*1>D4<2>/ + 0#Degree/0#D4/ grows a conjunct melody; (2) 0#E4<1..7><8><9*>/ + 0#Chord/0#TEmEmEmEmEmEmEm/
      -> 0#E4<1..7>/0#TEmEmEmEmEmEmEm/ + 0#<8><9*>/ + 0#Chord/ cuts off a bar and gives it a chord containing
      its first note; (6) and (7) replace an avoid note via Dummy; (8) concatenates two bar sequences
      along a cadence; (9) cuts out a four-bar phrase that starts on a tonic bar and terminates it with
      Start and Stop; (10) detaches a leading non-tonic bar, which is reused.

      '
    notes: 'Rule counts: 8 note rules (one per pitch), 38 chord rules (one per chord object and per note
      of the triad, C counting as C4 and C5), 8 avoid rules (G and Bm need one each for C4 and C5) plus
      1 Dummy rule, 6 cadence rules, 1 phrase rule and 3 detach rules = 65, the published total. No rule
      has a rate: the paper models only qualitative behaviour.

      '
  A:
    reactor: well-stirred-multiset
    dilution: none; the multiset is closed apart from the objects the rules release, and finished phrases
      accumulate as final products
    notes: 'Random collision (paper section 5): molecules are selected at random and collide to react,
      one possible computation of the nondeterministic algorithm. Chemart draws a rule with a weight equal
      to its number of ordered reactant choices, then the reactants in proportion to their copies and
      one match uniformly, and stops after `phrases` finished phrases.

      '
  params:
  - name: mode
    type: enum
    default: homophonic
    choices:
    - homophonic
    role: structural
    meaning: 'which published system to run: homophonic is the phrase-with-chords system of [592]; the
      polyphonic system of [854] is not reconstructed (see decisions), so it is not offered as a choice'
  - name: cadences
    type: enum
    default: published
    choices:
    - published
    - with-s-t
    role: structural
    meaning: 'cadence rules of step 4: published gives the six of section 4.3 (T-D2, T-D, T-S, D-T, D2-D,
      D2-T), which reproduces the published total of 65 rules; with-s-t adds S-T (66 rules), which the
      typical cadence T-S-T and the phrase of figure 3(1) require'
  - name: avoid_notes
    type: bool
    default: true
    role: selection
    meaning: include the avoid-note rules of section 3.3 that replace a note dissonant with the bar's
      chord (8 rules plus the Dummy rule); false drops them and leaves 56 rules
  - name: notes_per_bar
    type: int
    default: 8
    min: 2
    max: 32
    range: 'published: 8 eighth notes in a bar'
    role: structural
    meaning: notes in one bar; it sizes the chord line and the wildcard runs of rules (2), (8), (9) and
      (10)
  - name: bars_per_phrase
    type: int
    default: 4
    min: 1
    max: 16
    range: 'published: four-bar phrases'
    role: structural
    meaning: bars cut out as one phrase by rule (9)
  - name: copies
    type: int
    default: 1
    min: 1
    max: 1000
    role: population
    meaning: multiplies every count of the published initial multiset (43 kinds, 1826 objects at 1)
  - name: steps
    type: int
    default: 20000
    min: 0
    max: 10000000
    role: population
    meaning: maximum number of collisions of the recorded run; failed draws (too few copies, or products
      equal to reactants) are included
  - name: phrases
    type: int
    default: 1
    min: 0
    max: 1000
    range: the paper's runs collect three to five phrases in about an hour
    role: population
    meaning: stop once this many finished phrases are in the multiset; 0 runs the full number of steps
  provides:
  - topology
  - stoichiometry
  - initial-state
  - mass-conservation
  - sequence-structure-function
  fidelity: reconstructed
  sources:
  - Banzhaf, W. & Yamamoto, L. (2015). Artificial Chemistries, section 16.4 (melodies as patterns, combination
    rules, random factors, chords in the patterns, stricter rules filtering out disharmonic combinations,
    well-stirred reactor tank) and figure 16.11 (three homophonic phrases from [592], three polyphonic
    phrases from [854]).
  - 'Miura, T. & Tominaga, K. (2006). An approach to algorithmic music composition with an artificial
    chemistry. In Explorations in the Complexity of Possible Life (Proceedings of GWAL-7), pp. 21-30.
    Aka/IOS Press (book [592]). Camera-ready PDF recovered from the authors'' site: https://web.archive.org/web/20061028202625id_/http://www.tomilab.net/alife/paper/MiuraMusic2CR.pdf
    - section 2 (notation, matching and recombination examples), section 3 (the five-step algorithm, avoid
    pitches, cadence rules), section 4 (elements, initial objects with counts, rules 1-10, figures 1 and
    2), section 5 (simulator, results, figure 3).'
  - 'Tominaga, K. (2008). Automatic music composition by an artificial chemistry (lab page, book ref [2],
    http://www.tomilab.net/alife/music/): the generated samples, four-bar 8th-note phrases, and ''the
    following phrase is composed of two upper and lower melodies, both generated by the artificial chemistry''
    for the polyphonic work. Archived at https://web.archive.org/web/20090106131135id_/http://www.tomilab.net/alife/music/index.html.en'
  - 'Fernandez, J. D. & Vico, F. (2013). AI methods in algorithmic composition: a comprehensive survey.
    JAIR 48:513-582, p. 554 and table: the only open description of [854] found - ''Tominaga and Setomoto
    (2008) used this method, encoding polyphonic compositions in the strings and musical rules for counterpoint
    in the reaction rules of the artificial chemistry: starting from a set of simple strings, the system
    generated progressively more complex ones''. https://www.jair.org/index.php/jair/article/download/10845/25883'
  decisions:
  - 'Attribution: the v1 entry and the assignment named ''Miyamoto & Tominaga'' and ''Tominaga et al.'';
    the book''s bibliography has [592] T. Miura and K. Tominaga (GWAL-2006) and [854] K. Tominaga and
    M. Setomoto (EvoWorkshops 2008, LNCS 4974, pp. 463-472, doi 10.1007/978-3-540-78761-7_49). The bibliography
    is followed.'
  - The book (16.4) describes the approach only qualitatively, so everything is reconstructed from the
    2006 camera-ready paper, recovered from the Wayback Machine copy of the authors' site (tomilab.net
    no longer resolves). The paper's own artificial chemistry is Tominaga's pattern-matching-and-recombination
    chemistry, catalogued separately as tominaga-stacked-strings; the music system is re-implemented here
    in the 2006 paper's own notation (<1>, <*1>, <1*>, <1..7>), which that module's parser does not accept
    because music elements contain digits (C4, D2).
  - 'The polyphonic system of [854] is not implemented: the paper is paywalled (Springer LNCS 4974, no
    open version in Unpaywall, OpenAlex, CORE or the Wayback copy of the authors'' site, which links only
    the MIDI results) and the book gives no detail. Only its existence and the survey-level description
    are recorded in sources; the mode parameter therefore keeps the single published choice homophonic
    rather than inventing a polyphonic rule set.'
  - The paper states '24 kinds of elements' and lists exactly 24 (8 notes, 7 chords, 4 functions, 5 control
    elements) but its own initial objects also use Dummy, so the implementation has 25 element kinds.
    The published 24 is the listed set.
  - 'The three published totals of section 4 are reproduced exactly: 43 kinds of initial objects, 1826
    objects in total (14 conjunct-motion objects at 100, 11 chord objects at 20, 1 Avoid/Dummy at 10,
    8 Avoid/note at 10, 1 StartStop at 100, 8 seed notes at 2) and 65 rules (8 + 38 + 8 + 1 + 6 + 1 +
    3). The 65 fixes two things the paper leaves implicit: the chord rules are one per chord object and
    per note of its triad with C counted as both C4 and C5 (38), and the avoid rules of G and Bm need
    one rule each for C4 and C5 (8), as their avoid pitch is given as ''C (where C means both C4 and C5)''.'
  - Cadence discrepancy, exposed as the cadences parameter. Section 3.4 lists T-S-T among the typical
    cadences, but its four numbered rules only add T after D or D2, and section 4.3 gives rules for T-D2,
    T-D, T-S, D-T, D2-D and D2-T - six rules, which is what the published total of 65 requires. Under
    those six, the phrase of figure 3(1) (Am, Am, C, G) is not derivable under any function assignment,
    because it needs S-T; figure 1 (C, G, C, G) and figures 3(2) (Em, Dm, G, Em) and 3(3) (C, Bm, Am,
    F) are derivable. Default published keeps the six and the rule count; with-s-t adds S-T (66 rules)
    and makes figure 3(1) derivable.
  - 'Section 5 states that a phrase terminated by Start and Stop ''is no longer recombined by any rule''.
    That is exactly true for a phrase without avoid notes, which is the case of figure 1 (verified: no
    rule matches it); a phrase that still carries an avoid note is still matched by rule (6) and can be
    repaired. This is not treated as an erratum: section 6 only claims that a bar has ''little'' dissonance,
    and rule (9) does not require the avoid notes to have been replaced first.'
  - Wildcard numbers are generated, not copied. For the default 8 notes per bar and 4 bars per phrase
    the generated rules (1), (2), (6), (7), (8), (9) and (10) come out character for character as printed
    in the paper (checked by a test); other bar sizes reuse the same scheme.
  - 'Reactor: the paper''s simulator (Cocoa/Objective-C, random collision) is not available and the authors
    themselves state it ''lacks sufficient theoretical foundation for simulating quantitative behaviour''
    and report only the products, not time series. Chemart therefore samples a rule with a weight equal
    to its number of ordered reactant choices, draws reactants in proportion to their copies and one match
    uniformly, and records the reactions that fired with their firing counts. No rates are attached anywhere,
    and no time series is claimed.'
  - 'Run length: the paper''s runs produce three to five phrases in about an hour on a PowerPC G5 and
    have no terminating condition. Chemart stops after `phrases` finished phrases (default 1, reached
    in about 0.2 s), or after `steps` collisions; phrases=0 runs the whole budget. The published wall-clock
    times are not reproduced.'
  - Initial counts are the published ones, which the paper calls 'somewhat arbitrary', chosen so that
    a few phrases appear in reasonable time; copies scales them uniformly.
  - 'v1 parameters: mode is kept with its single published choice, the callable harmony_filter becomes
    avoid_notes (the section 3.3 rules) together with the cadences choice (the section 3.4 filter), and
    the matrix seed_patterns becomes the published initial multiset with copies.'
  - Rules conserve elements ('conserving elements just like a chemical reaction does', section 2), so
    extras.conservation carries one conservation vector per element kind; the tests check m^T (P - R)
    = 0 for each of them.
  reference_impl: none public; the authors' simulator was a Cocoa/Objective-C application and the lab
    site tomilab.net is gone
  phenomena:
  - 'composes four-bar phrases in a defined style without any fitness function: every generated phrase
    has a conjunct melody, a chord per bar that contains the bar''s first note, few avoid notes, a cadence-conforming
    chord progression and a tonic first bar (paper sections 3 and 6)'
  - 'a phrase terminated by Start and Stop is a final product: no rule matches the phrase of figure 1
    any more'
  - jumps in an otherwise conjunct melody come from avoid notes being replaced with random notes (section
    5, visible in figures 1 and 3)
  - 'a sequence of bars that starts with a non-tonic bar is not discarded: the leading bar is detached
    by rule (10) and reused (figure 2, steps 10-12)'
  - every rule conserves elements, so the multiset's element content is invariant
  - the nondeterminism of the chemistry supplies the randomness the composition needs, and several phrases
    grow in parallel in the same reactor
  notes: 'The module also exports parse_object, parse_pattern, match, Rule (with apply), rule_set, initial_pool,
    read_bars, describe and the Reactor for direct use. Book figure 16.11 shows three homophonic phrases
    from this system (left) and three polyphonic phrases from [854] (right); only the homophonic system
    is implemented.

    '