Class: Musa::Transcriptors::FromGDV::ToMIDI::Mordent

Inherits:
Musa::Transcription::FeatureTranscriptor show all
Defined in:
lib/musa-dsl/transcription/from-gdv-to-midi.rb

Overview

Mordent transcriptor for MIDI playback.

Expands mordent ornaments into a three-note sequence: main note, adjacent note (upper or lower), then main note. The mordent is a quick ornament typically used to emphasize a note.

Mordent Types

  • .mor or .mor(:up) - Upper mordent (main, upper neighbor, main)
  • .mor(:down) or .mor(:low) - Lower mordent (main, lower neighbor, main)

Processing

Given .mor on a note:

{ grade: 0, duration: 1r, mor: true }

Expands to three notes:

[
  { grade: 0, duration: 1/16r },    # Main note (short)
  { grade: 1, duration: 1/16r },    # Upper neighbor (short)
  { grade: 0, duration: 7/8r }      # Main note (remaining duration)
]

Duration Calculation

Short notes duration: base_duration * duration_factor (default 1/4) Final note gets remaining duration: original - 2 * short_duration

Process: .mor

Examples:

Upper mordent

mor = Mordent.new(duration_factor: 1/4r)
gdv = { grade: 0, duration: 1r, mor: true }
result = mor.transcript(gdv, base_duration: 1/4r, tick_duration: 1/96r)
# => [
#   { grade: 0, duration: 1/16r },
#   { grade: 1, duration: 1/16r },
#   { grade: 0, duration: 7/8r }
# ]

Lower mordent

gdv = { grade: 0, duration: 1r, mor: :down }
# Uses lower neighbor (grade: -1)

Instance Method Summary collapse

Constructor Details

#initialize(duration_factor: nil) ⇒ Mordent

Creates mordent transcriptor.

Parameters:

  • duration_factor (Rational) (defaults to: nil) —

    factor for ornament note duration relative to base_duration (default: 1/4)



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# File 'lib/musa-dsl/transcription/from-gdv-to-midi.rb', line 230

def initialize(duration_factor: nil)
  @duration_factor = duration_factor || 1/4r
end

Instance Method Details

#transcript(gdv, base_duration:, tick_duration:) ⇒ Array<Hash>, Hash

Transcribes mordent to three-note sequence.

Parameters:

  • gdv (Hash) —

    GDV event possibly containing :mor

  • base_duration (Rational) —

    base duration unit

  • tick_duration (Rational) —

    minimum tick duration

Returns:

  • (Array<Hash>, Hash) —

    array with mordent notes, or unchanged event



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# File 'lib/musa-dsl/transcription/from-gdv-to-midi.rb', line 243

def transcript(gdv, base_duration:, tick_duration:)
  mor = gdv.delete :mor

  if mor
    direction = :up

    check(mor) do |mor|
      case mor
      when true, :up
        direction = :up
      when :down, :low
        direction = :down
      end
    end

    short_duration = [base_duration * @duration_factor, tick_duration].max

    gdvs = []

    gdvs << gdv.clone.tap { |gdv| gdv[:duration] = short_duration }

    case direction
    when :up
      gdvs << gdv.clone.tap { |gdv| gdv[:grade] += 1; gdv[:duration] = short_duration }
    when :down
      gdvs << gdv.clone.tap { |gdv| gdv[:grade] -= 1; gdv[:duration] = short_duration }
    end

    gdvs << gdv.clone.tap { |gdv| gdv[:duration] -= 2 * short_duration }

    super gdvs, base_duration: base_duration, tick_duration: tick_duration
  else
    super
  end
end