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Draft states provide first-class support for intentionally incomplete content during iterative composition. See: /MRS-Specification-RFC#11-data-model

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The Problem

Early-stage composition is inherently incomplete:
  • You know the harmony before the orchestration
  • You have a melody before the accompaniment
  • You have rhythm sketches before final pitches
Without draft states:
  1. Forced completeness leads to hallucinated filler
  2. Empty measures are ambiguous (rest or TBD?)
  3. Intent is lost — an empty measure might mean “rest” or “to be filled”

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Placeholder Primitives

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Placeholder Region

Mark a region as intentionally incomplete: 
(placeholder
  :id #uuid "..."
  :measures #uuid "..." #uuid "..."
  :instruments [violin-1 violin-2 viola cello]
  :intent accompaniment
  :description "Strings accompany flute melody")
FieldDescription
:measuresUUID range
:instrumentsAffected instruments
:intentWhat kind of content is planned
:descriptionHuman-readable description

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Intent Types

IntentDescription
:melodyMelodic content TBD
:accompanimentAccompaniment pattern TBD
:countermelodyCounter-line TBD
:harmonyHarmonic content TBD
:orchestrationOrchestration TBD
:textureGeneral texture/pad TBD
:rhythmRhythmic pattern TBD

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Sketch Rhythm

Provide rhythm without final pitches: 
(sketch-rhythm
  :id #uuid "..."
  :measure #uuid "..."
  :instrument flute-1
  :voice v1
  :rhythm [q e e h]
  :description "Main theme rhythm, pitches TBD")

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Harmonic Sketch

Provide harmony without voicing: 
(harmony-plan
  (region :measures #uuid "..." #uuid "..."
    (chord :beat 0 :symbol Cm)
    (chord :beat 2 :symbol Fm)
    (chord :beat 0 :symbol G7)))

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Validation Levels

MRS supports validation levels to accommodate draft states:
LevelAllows
strictNo placeholders; all content complete
permissivePlaceholders allowed; validates what exists
sketchMinimal validation; for early drafts

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Strict Validation

(meta
  :validation-level strict
  ...)
All measures must have complete content. Placeholders are errors.

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Permissive Validation

(meta
  :validation-level permissive
  ...)
Placeholders are valid. Validates:
  • Existing content is well-formed
  • References are valid
  • Placeholder intents are recognized

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Sketch Validation

(meta
  :validation-level sketch
  ...)
Minimal validation for early drafts:
  • Basic syntax
  • UUID validity
  • No content requirements

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Example: From Sketch to Complete

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Stage 1: Harmony Plan Only

(mrs-s 1.0
  (meta :title "New Piece" :validation-level sketch)
  (players ...)
  (instruments ...)
  (measures
    (measure :id #uuid "..." :number 1 :beat-start 0 :time 4/4
      (placeholder :instruments [flute-1 clarinet-bb violin-1]
                   :intent orchestration
                   :description "Full orchestration TBD")))
  (spans)
  (harmony-plan
    (region :measures #uuid "..." #uuid "..."
      (chord :beat 0 :symbol Cm)
      (chord :beat 2 :symbol Fm))))

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Stage 2: Melody Added

(measure :id #uuid "..." :number 1 :beat-start 0 :time 4/4
  (flute-1
    (v1
      (: 0 Eb5.q :id #uuid "...")
      (: 1 D5.q :id #uuid "...")
      (: 2 Eb5.e :id #uuid "...")
      (: 2+1/2 F5.e :id #uuid "...")
      (: 3 G5.q :id #uuid "...")))
  (placeholder :instruments [clarinet-bb violin-1]
               :intent accompaniment
               :description "Accompaniment to flute melody"))

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Stage 3: Complete

(measure :id #uuid "..." :number 1 :beat-start 0 :time 4/4
  (flute-1
    (v1 (: 0 Eb5.q :id #uuid "...") ...))
  (clarinet-bb
    (v1 (: 0 G4.h :id #uuid "...") ...))
  (violin-1
    (v1 (: 0 C4.q :id #uuid "...") ...)))

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Operations on Placeholders

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Resolve Placeholder

Replace placeholder with actual content: 
(resolve-placeholder
  :placeholder-id #uuid "..."
  :content
    ((create-event :tmp-id "e1" :measure #uuid "..." 
                   :instrument clarinet-bb :voice v1
                   :beat 0 :pitch G4 :duration h)
     ...))

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Refine Placeholder

Add detail without fully resolving: 
(refine-placeholder
  :placeholder-id #uuid "..."
  :add-sketch-rhythm
    (sketch-rhythm :instrument clarinet-bb :voice v1
                   :rhythm [h h]))

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Checkpoints and Placeholders

Checkpoints can require placeholder resolution: 
(checkpoint
  :id "orchestration-complete"
  :requires
    ((no-placeholders :scope :all)))
After this checkpoint, placeholders are validation errors.