Module: Musa::Neumas::Decoders

Defined in:
lib/musa-dsl/neumas/neuma-decoder.rb,
lib/musa-dsl/neumas/neuma-gdv-decoder.rb,
lib/musa-dsl/neumas/neuma-gdvd-decoder.rb

Overview

Neuma decoder infrastructure for converting neuma notation to musical events.

Provides base classes for decoding neuma notation (a musical representation format) into GDV (Grade-Duration-Velocity) events. The decoder system supports differential decoding where each event is interpreted relative to the previous event.

Architecture Overview

Decoder Hierarchy

ProtoDecoder (abstract)
  └── DifferentialDecoder (abstract)
        └── Decoder (stateful base)
              ├── NeumaDecoder (GDV output)
              └── NeumaDifferentialDecoder (GDVD output)

Key Concepts

  1. Differential Decoding: Each neuma is interpreted relative to previous state

    • Grade: +2 means "2 steps up from last note"
    • Duration: _2 means "double the base duration"

  2. Stateful Processing: Decoders maintain @last state for differential interpretation

  3. Subcontexts: Create independent decoder contexts for nested structures

  4. Transcription Integration: Optional transcriptor for post-processing (ornaments, etc.)

Processing Pipeline

Neuma Input → process() → apply() → Transcriptor → GDV Output
                 ↓           ↓
             Prepare     Apply to
             attributes   last state

Neuma Notation

Neumas are text-based musical notation:

"(0) (+2) (+2) (-1)"        # Grade sequence (scale degrees)
"_ _2 _/2"          # Duration modifiers
"(0 st) (0 tr) (0 mor)"  # Articulation/ornament modifiers, inside the neuma
"(+1_/4)+2_"        # Appogiatura (grace note) + main note

Decoders are used by the neuma parsing system:

decoder = Musa::Neumas::Decoders::NeumaDecoder.new(
  scale,
  base_duration: 1/4r,
  transcriptor: transcriptor
)

# Parse and decode neuma string
neumas = "(0) (+2) (+2) (-1) (0)".to_neumas
neumas.each { |neuma| decoder.decode(neuma) }

Examples:

Basic usage

See Also:

Defined Under Namespace

Classes: Decoder, DifferentialDecoder, NeumaDecoder, NeumaDifferentialDecoder, ProtoDecoder