Structural Index

The Structural Index provides agents with global awareness of the score’s structure without requiring the full content. See: /MRS-Specification-RFC#9-structural-index

Purpose

Agents operating on a focused region need to understand:

Where they are in the overall form
Key areas and tempo changes
What instruments are active
Rehearsal mark locations

The Structural Index provides this without loading the entire score.

Index Structure

(structural-index
  :hash "sha256:abc123..."
  :source-hash "sha256:def456..."
  
  :form
    (sections
      (section :type exposition :measures #uuid "..." #uuid "..." :display [1 64])
      (section :type development :measures #uuid "..." #uuid "..." :display [65 120])
      (section :type recapitulation :measures #uuid "..." #uuid "..." :display [121 180]))
  
  :key-areas
    ((region :key C :mode minor :measures #uuid "..." #uuid "...")
     (region :key Eb :mode major :measures #uuid "..." #uuid "...")
     (region :key G :mode minor :measures #uuid "..." #uuid "..."))
  
  :tempo-map
    ((tempo :bpm 120 :measures #uuid "..." #uuid "...")
     (tempo :bpm 80 :text "Adagio" :measures #uuid "..." #uuid "..."))
  
  :players-summary
    ((player woodwind-2 :instruments [flute-2 piccolo] :active-measures [...])
     (player clarinet-1 :instruments [clarinet-bb] :active-measures [...]))
  
  :rehearsal-marks
    ((mark "A" :measure #uuid "..." :number 16)
     (mark "B" :measure #uuid "..." :number 32)
     (mark "C" :measure #uuid "..." :number 48))
  
  :total-measures 180
  :total-duration "12:34")

Index Fields

Form

:form
  (sections
    (section :type exposition :measures #uuid "..." #uuid "..." :display [1 64])
    (section :type development :measures #uuid "..." #uuid "..." :display [65 120]))

Field	Description
`:type`	Section type (exposition, development, coda, etc.)
`:measures`	UUID range
`:display`	Human-readable measure numbers

Key Areas

:key-areas
  ((region :key C :mode minor :measures #uuid "..." #uuid "...")
   (region :key Eb :mode major :measures #uuid "..." #uuid "..."))

Tempo Map

:tempo-map
  ((tempo :bpm 120 :measures #uuid "..." #uuid "...")
   (tempo :bpm 80 :text "Adagio" :measures #uuid "..." #uuid "..."))

Players Summary

:players-summary
  ((player woodwind-2 :instruments [flute-2 piccolo] :active-measures [...])
   (player clarinet-1 :instruments [clarinet-bb] :active-measures [...]))

Rehearsal Marks

:rehearsal-marks
  ((mark "A" :measure #uuid "..." :number 16)
   (mark "B" :measure #uuid "..." :number 32))

Index Derivation

The structural index can be:

Source	Description
Derived	Automatically computed from the score
Enhanced	Enriched by analytical overlays
Annotated	Manually labeled (form, section names)

Automatically Derived

Measure count
Key signature changes
Tempo changes
Rehearsal marks
Player/instrument activity

Requires Analysis/Annotation

Form labels (exposition, development, etc.)
Thematic regions
Phrase structure

Usage in Working Sets

Working Set Envelopes include a reference to the structural index:

(working-set
  ...
  :structural-index-ref "sha256:abc123..."
  ...)

Agents can use this to:

Understand where they are in the form
Check what other instruments are active
Find rehearsal marks for reference
Understand key and tempo context

Index vs Context Views

Structural Index	Context Views
Global overview	Task-specific detail
Read-only summary	May include content
Always available	Selected per task
Score-level info	Region-level info

Both are used together: the index for global awareness, context views for task-specific information.

Overview

MRS-S Format

Agent Workflows

Model & Validation

Purpose

Index Structure

Index Fields

Form

Key Areas

Tempo Map

Players Summary

Rehearsal Marks

Index Derivation

Automatically Derived

Requires Analysis/Annotation

Usage in Working Sets

Index vs Context Views

​Purpose

​Index Structure

​Index Fields

​Form

​Key Areas

​Tempo Map

​Players Summary

​Rehearsal Marks

​Index Derivation

​Automatically Derived

​Requires Analysis/Annotation

​Usage in Working Sets

​Index vs Context Views

Purpose

Index Structure

Index Fields

Form

Key Areas

Tempo Map

Players Summary

Rehearsal Marks

Index Derivation

Automatically Derived

Requires Analysis/Annotation

Usage in Working Sets

Index vs Context Views