MRS-S Measures & Events

See: /MRS-Specification-RFC#4-mrs-s-the-canonical-storage-format

Measures Section

(measures
  (measure 
    :id #uuid "018c3f40-0001-7890-abcd-ef1234567890"
    :number 1
    :beat-start 0
    :time 4/4
    :key C :mode minor
    :tempo 120
    
    (flute-1
      (v1
        (: 0 C5.q :id #uuid "018c3f2a-0001-...")
        (: 1 D5.q :id #uuid "018c3f2a-0002-...")
        (: 2 E5.h :id #uuid "018c3f2a-0003-...")))
    
    (clarinet-bb
      (v1
        (: 0 r.w :id #uuid "018c3f2a-0010-...")))))

Measure Attributes

Attribute	Required	Type	Description
`:id`	YES	UUIDv7	Stable identifier
`:number`	YES	integer	Display number (can have gaps)
`:beat-start`	YES	rational	Absolute beat position (orchestrator-computed)
`:time`	NO	fraction	Time signature (inherits if omitted)
`:key`	NO	pitch-class	Key signature (inherits if omitted)
`:mode`	NO	keyword	Mode (inherits if omitted)
`:tempo`	NO	integer	Tempo in BPM (inherits if omitted)
`:tempo-text`	NO	string	Tempo marking text
`:rehearsal`	NO	string	Rehearsal mark
`:barline-left`	NO	keyword	Left barline type
`:barline-right`	NO	keyword	Right barline type

Attribute Inheritance

Attribute	Inherits?
`:time`	Yes, until changed
`:key`, `:mode`	Yes, until changed
`:tempo`, `:tempo-text`	Yes, until changed
`:rehearsal`	No (single-measure)
`:barline-*`	No (per-measure)

Barline Types

none single double final
repeat-start repeat-end repeat-both

Instrument Content

Within a measure, content is organized by instrument:

(measure :id #uuid "..." :number 1
  (flute-1
    (v1 ...))
  
  (clarinet-bb
    (v1 ...)
    (v2 ...))
  
  (piano
    (:rh (v1 ...))
    (:lh (v1 ...))))

Voice Naming

Instrument Type	Voice Names
Single-staff	`v1` through `v4`
Keyboard	`:rh`/`:lh` containing `v1`, `v2`, etc.

Event Syntax

(: <beat> <pitch-expr> :id <uuid> <properties>*)

Component	Description
`:`	Event marker
`<beat>`	Beat position within measure (0-indexed, rational)
`<pitch-expr>`	Pitch, chord, or rest
`:id`	Stable UUIDv7 identifier (REQUIRED)
`<properties>`	Optional `:keyword value` pairs

Examples

(: 0 C5.q :id #uuid "...")           ; C5 quarter on beat 0
(: 1 Eb4.e :id #uuid "..." :dyn f)   ; Eb4 eighth on beat 1, forte
(: 2+1/2 [C4 E4 G4].q :id #uuid "...") ; Chord on beat 2.5
(: 3 r.q :id #uuid "...")            ; Quarter rest on beat 3

Beat Position

Beat positions are exact rationals relative to measure start (0-indexed):

4/4 time:
  0      = Beat 1 (downbeat)
  1      = Beat 2
  2      = Beat 3
  3      = Beat 4
  0+1/2  = "And" of beat 1
  1+3/4  = Fourth sixteenth of beat 2

6/8 time (compound):
  0      = Downbeat
  1      = Dotted quarter 2
  0+1/3  = First eighth subdivision

Canonical form: Use integers for whole beats, mixed numbers for fractions:

0, 1, 2 (integers)
2+1/2 (two and a half)
0+1/3 (one third)

Decimal literals (2.5) are NOT permitted.

Pitch Expression

Single Note

C4.q        ; C4 quarter note
Eb5.h       ; E-flat 5 half note
F#3.e       ; F-sharp 3 eighth note
Bbb4.w      ; B double-flat 4 whole note
Cx4.s       ; C double-sharp 4 sixteenth note

Chord

[C4 E4 G4].q      ; C major triad, quarter
[D3 F#3 A3 C4].h  ; D7 chord, half note

Rest

r.q         ; Quarter rest
r.h         ; Half rest
r.w         ; Whole rest

Duration Codes

Code	Name	Beats
`w`	Whole	4
`h`	Half	2
`q`	Quarter	1
`e`	Eighth	1/2
`s`	Sixteenth	1/4
`t`	Thirty-second	1/8
`x`	Sixty-fourth	1/16

Dotted Durations

Code	Name	Beats
`q.`	Dotted quarter	3/2
`h.`	Dotted half	3
`q..`	Double-dotted quarter	7/4

Event Properties

(: 0 G4.q 
  :id #uuid "018c3f2a-..."
  :dyn ff
  :art staccato
  :orn trill
  :tech pizz
  :lyrics [{:text "Hal-" :syllabic begin}]
  :grace true
  :cue true
  :cue-source violin-1)

Property	Type	Description
`:dyn`	keyword	Dynamic marking
`:art`	keyword	Articulation
`:orn`	keyword	Ornament
`:tech`	keyword	Playing technique
`:lyrics`	list	Lyric syllables
`:grace`	boolean	Grace note
`:cue`	boolean	Cue note
`:cue-source`	instrument-id	Source for cue

Dynamics

pppp ppp pp p mp mf f ff fff ffff
sfz sfp sffz fz rf rfz fp sf

Articulations

staccato staccatissimo tenuto accent marcato
portato fermata breath caesura

Ornaments

trill mordent mordent-inverted
turn turn-inverted tremolo
arpeggio glissando

Techniques (Strings)

arco pizz pizz-snap
pont tasto normale
harm harm-natural harm-artificial
spicc detache martele

Techniques (Winds)

tongue double-tongue triple-tongue flutter
cuivre stopped open mute-straight

Tuplets

(tuplet 3:2 q
  (: 0 C4.e :id #uuid "...")
  (: 0+1/3 D4.e :id #uuid "...")
  (: 0+2/3 E4.e :id #uuid "..."))

Triplet: 3 notes in the space of 2 quarters.

Grace Notes

(grace :type acciaccatura
  (: 0 D5.s :id #uuid "..."))

(: 0 C5.q :id #uuid "...")  ; Main note

Grace types: acciaccatura, appoggiatura

Overview

MRS-S Format

Agent Workflows

Model & Validation

MRS-S Measures & Events

Measures Section

Measure Attributes

Attribute Inheritance

Barline Types

Instrument Content

Voice Naming

Event Syntax

Examples

Beat Position

Pitch Expression

Single Note

Chord

Rest

Duration Codes

Dotted Durations

Event Properties

Dynamics

Articulations

Ornaments

Techniques (Strings)

Techniques (Winds)

Tuplets

Grace Notes

​Measures Section

​Measure Attributes

​Attribute Inheritance

​Barline Types

​Instrument Content

​Voice Naming

​Event Syntax

​Examples

​Beat Position

​Pitch Expression

​Single Note

​Chord

​Rest

​Duration Codes

​Dotted Durations

​Event Properties

​Dynamics

​Articulations

​Ornaments

​Techniques (Strings)

​Techniques (Winds)

​Tuplets

​Grace Notes

Measures Section

Measure Attributes

Attribute Inheritance

Barline Types

Instrument Content

Voice Naming

Event Syntax

Examples

Beat Position

Pitch Expression

Single Note

Chord

Rest

Duration Codes

Dotted Durations

Event Properties

Dynamics

Articulations

Ornaments

Techniques (Strings)

Techniques (Winds)

Tuplets

Grace Notes