Class: HeadMusic::Style::Guides::ContourMelody

Inherits:
SpeciesMelody show all
Defined in:
lib/head_music/style/guides/contour_melody.rb

Overview

A free diatonic melody targeting a specific contour. Configured rather than subclassed: ContourMelody.with(contour: :arch, minimum_melodic_intervals: 2).

Deliberately NOT a subclass of DiatonicMelody, even though it builds on that guide’s ruleset. Ruby resolves ::RULESET up the ancestor chain, so inheriting from DiatonicMelody would leave ContourMelody::RULESET silently returning the plain diatonic ruleset – no contour rule, no motion gate, unweighted peers, and a plausible-looking fitness. The ruleset is reached fully-qualified below instead, which keeps the constant genuinely absent here.

Constant Summary collapse

PEER_WEIGHT_BUDGET =

The non-gate peers of a contour guide share phi^-2 of rubric weight, so that with Contoured at its default weight of phi^-1 (and phi^-1 + phi^-2 = 1), a wrong contour on an otherwise perfect line grades exactly phi^-1.

HeadMusic::GOLDEN_RATIO_INVERSE**2

Class Method Summary collapse

Class Method Details

.analyze(voice) ⇒ Object

Guide.get passes through anything answering analyze, so naming this class instead of a registry key reaches Analysis and would otherwise fail at the first annotation with a bare “missing keyword: :contour”. Now that the six contour subclasses are gone, that is the likeliest way to hold this wrong, so the error names both ways to hold it right.

Raises:

  • (ArgumentError) 


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# File 'lib/head_music/style/guides/contour_melody.rb', line 41

def self.analyze(voice)
  raise ArgumentError,
    "#{name} requires configuration. " \
    "Use #{name}.with(contour: :arch, minimum_melodic_intervals: 2) " \
    'or HeadMusic::Style::Guide.get("arch_contour_melody").'
end

.ruleset(contour:, minimum_melodic_intervals: nil) ⇒ Object

An optional motion gate excludes non-attempts; nil omits it, so a static contour can legitimately repeat a single pitch.



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# File 'lib/head_music/style/guides/contour_melody.rb', line 50

def self.ruleset(contour:, minimum_melodic_intervals: nil)
  motion_gate =
    minimum_melodic_intervals &&
    HeadMusic::Style::Guidelines::MinimumMelodicIntervals.with(minimum_melodic_intervals)
  [
    *GATES,
    motion_gate,
    *WEIGHTED_PEERS,
    HeadMusic::Style::Guidelines::Contoured.with(contour)
  ].compact.freeze
end

.with(contour:, minimum_melodic_intervals: nil) ⇒ Object

Normalizes eagerly so an invalid contour raises HERE, at configuration time, rather than at analysis. Required keyword, so an omitted or misspelled option name raises too.



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# File 'lib/head_music/style/guides/contour_melody.rb', line 29

def self.with(contour:, minimum_melodic_intervals: nil)
  super(
    contour: HeadMusic::Style::Guidelines::Contoured.normalized_contour(contour),
    minimum_melodic_intervals: minimum_melodic_intervals
  )
end