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Use when composing music with the music-server MCP tools. Covers note syntax, tool workflow, and composition patterns.
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Based on SOC occupation classification
| name | music-composition |
| description | Use when composing music with the music-server MCP tools. Covers note syntax, tool workflow, and composition patterns. |
You have 47 MCP tools for building compositions from scratch. This skill covers the syntax, tool flow, and patterns.
Before doing anything else, load all music-server schemas in one batch ToolSearch call:
ToolSearch: "mcp music-server" (max_results=50)
Do this once at the start of the session. MCP tool schemas are deferred — calling any tool without loading its schema first causes an error and forces a mid-composition round-trip.
Notes are whitespace-separated tokens: pitch/duration
Pitch: standard name + optional accidental + octave: C4, F#3, Bb5, Eb4
Rests: r/q, r/h, r/e etc.
Chords: angle brackets around space-separated pitches, followed by /duration:
<C4 E4 G4>/q → C major triad, quarter note
<Eb3 G3 Bb3>/h → Eb major triad, half note
<D3 F3 A3 C4>/q → Dm7 chord, quarter note
Use chords for pad stabs, gospel organ, jazz voicings — any simultaneous pitches.
Duration codes:
| Code | Value |
|---|---|
w | whole |
h | half |
q | quarter |
e | eighth |
s | sixteenth |
dh | dotted half |
dq | dotted quarter |
de | dotted eighth |
h3 | half-note triplet (= 1/3 whole) |
q3 | quarter-note triplet (= 1/6 whole) |
e3 | eighth-note triplet (= 1/12 whole) |
s3 | sixteenth-note triplet (= 1/24 whole) |
Ties — append ~tie to hold a note into the next note of the same pitch (extends sound across bar lines):
C4/h~tie C4/q → C4 sounds for a dotted half total
G4/q~tie G4/e → G4 quarter + eighth tied together
Ties are rendered as ~ in LilyPond and extend NOTE_OFF in MIDI. Use for notes that cross bar lines or need durations not expressible as a single rhythmic value.
Per-note velocity — append ~vel:N (0–127) to override the voice-level dynamic for a single note:
C4/q~vel:100 D4/q E4/q~vel:40 # loud C, default D, quiet E
G4/h~vel:120~tie G4/q # very loud tied note
Useful for shaping phrases: push peak notes, pull back resolutions, accent approach tones. Takes precedence over voice.set_dynamics.
Articulations — append ~code after the duration:
| Suffix | Articulation | LilyPond mark | MIDI effect |
|---|---|---|---|
~stac | staccato | -. | 50% duration |
~acc | accent | -> | normal duration |
~ten | tenuto | -- | full duration |
~marc | marcato | -^ | 75% duration |
~leg | legato | (none) | full duration |
C4/q~stac D4/q E4/h # staccato C, normal D and E
<C4 E4 G4>/q~acc # accented chord stab
Use voice.set_articulation to apply an articulation to an entire voice at once.
Ornaments — append ~code after the duration (combinable with articulations and ~vel:N):
| Suffix | Ornament | LilyPond glyph | MIDI approximation |
|---|---|---|---|
~roll | roll (Irish/folk) | \trill | main–upper–main–lower–main |
~trill | trill | \trill | rapid main–upper alternation |
~mord | mordent (lower) | \mordent | main–lower–main |
~prall | pralltriller | \prall | main–upper–main |
A4/e~roll # rolled A eighth — classic Irish jig ornament
B4/q~trill # trilled B quarter
G4/e~mord # mordent on G eighth
MIDI uses semitone neighbors as pitch approximation (upper = +2, lower = −1). For accurate neighbor pitches, use explicit grace notes instead.
Grace notes — prefix {pitch ...} before the main note token. Pitches are space-separated; use standard pitch notation:
{G4}A4/q # single grace note G before A quarter
{G4 A4}B4/e # two grace notes before B eighth
Grace notes steal time from the front of the main note's sounding duration (~32nd note each). They appear as \grace { ... } in LilyPond.
Control Change (CC) events — point-in-time MIDI controller values placed inline in a voice sequence. Zero duration; do not advance time. MIDI only — invisible to LilyPond/MusicXML.
cc:pan:64 → center pan (CC 10, value 64)
cc:pan:20 → hard left
cc:pan:110 → hard right
cc:expr:100 → high expression (CC 11)
cc:expr:40 → low expression — fade down a phrase
cc:reverb:60 → medium reverb send (CC 91)
cc:mod:80 → modulation / vibrato depth (CC 1)
cc:sustain:127 → sustain pedal down (CC 64)
cc:sustain:0 → sustain pedal up
cc:11:80 → numeric form — same as cc:expr:80
Named aliases: mod (1), vol (7), pan (10), expr (11), sustain (64), reverb (91), chorus (93).
Expression CC (11) is how you shape dynamics on strings and brass — velocity sets the attack, expr shapes the phrase arc. Pan places instruments in the stereo field. Place CC events immediately before the note they should affect:
voice.create "strings" "cc:pan:30 cc:expr:60 C4/h cc:expr:90 E4/h cc:expr:70 G4/w"
Program Change events — mid-score instrument change within a voice. Zero duration. Use for switching patches (e.g. arco to pizzicato).
pc:45 → switch to Pizzicato Strings (0-indexed GM program; GM tables list this as #46)
pc:40 → switch back to Violin (0-indexed GM program; GM tables list this as #41)
voice.create "strings" "C4/h D4/h pc:45 E4/q F4/q G4/h"
Examples:
C4/q D4/q E4/q F4/q # four quarter notes
E4/e F#4/e G4/q r/q # eighths, quarter, rest
C4/dq D4/e E4/h # dotted quarter + eighth + half
<Eb3 G3 Bb3>/q <Ab3 C4 Eb4>/q # two chord stabs
C4/q~stac D4/q~stac r/e E4/e F4/q # staccato melody
score.set_metadata — set title, tempo (BPM), time signature ("4/4", "3/4")score.set_swing — enable swing quantization: ratio="2/3" (standard jazz), "3/5" (light), "0" to disablescore.set_tempo_change — gradual ritardando or accelerando across a bar span: start_bar, end_bar, to_bpm, optional curve="linear" (default) or "exponential" (more natural for rit.). Affects both MIDI playback and LilyPond notation.score.describe — inspect full composition state (voices, dynamics, articulations, instruments)score.assign_instrument — assign a voice to a GM instrument (see list below)score.clear — wipe everything and start freshvoice.create — create a named voice from a note sequencevoice.append — append more notes to an existing voicevoice.list — list all voices with bar counts, event counts, and durationvoice.measure_count — return the number of complete bars in a single voicevoice.set_dynamics — set volume for a voice: ppp pp p mp mf f ff fff (default: mf)voice.set_articulation — set articulation for a voice: staccato accent tenuto marcato legato. Optional from_bar / to_bar to scope to a bar range (e.g. make only the final phrase tenuto).voice.add_expression_curve — add a gradual CC 11 expression curve to a voice. Parameters: voice, start_bar, end_bar, from_value (0–127), to_value (0–127), curve (linear or exponential). Emits one CC 11 event per bar between start_bar and end_bar, interpolated from from_value to to_value. Use for crescendos, decrescendos, and phrase swells. Multiple curves on the same voice are additive. Example: voice.add_expression_curve voice=melody start_bar=9 end_bar=16 from_value=30 to_value=110 curve=exponential.voice.from_motif — Advanced: create a voice from a saved motif, optionally transformedvoice.delete — remove a voice from the compositionvoice.trim — truncate a voice to N bars, discarding everything aftervoice.set_bar — replace one bar's content: bar=N notes="C4/q D4/q E4/q F4/q". Use query.voice to inspect before editing.voice.replace_range — replace bars from_bar–to_bar (inclusive) with a new note sequence. The replacement doesn't have to fill the same number of bars.voice.replace_note — surgical fix: find the first note in bar N whose pitch matches old, replace it with new. Both old and new are full note tokens including duration, e.g. old="C4/q" new="D4/q". Use query.voice to inspect bar content first.query.voice — show the note sequence of a voicequery.motif — show the note sequence of a motiftransform.transpose — transpose by interval (e.g. "P5", "m3", "M2", "P8"), direction "up"/"down"transform.invert — Advanced: mirror pitches around an axis pitch (e.g. "C4")transform.retrograde — Advanced: reverse temporal ordertransform.augment — Advanced: scale all durations by a factor ("2/1"=double, "1/2"=halve)motif.save — save a slice of a voice as a named motif (start/end are 0-based note indices)voice.concat — concatenate multiple voices sequentially (voice_names: comma list, target_voice)voice.repeat — repeat a voice N times — great for ostinatos and drum loopsvoice.slice — Advanced: extract measures startMeasure–endMeasure (exclusive) from a voicevoice.pad_to_measure — Advanced: prepend rests so the voice starts at the given measure numberharmony.set_key — set the composition key, e.g. "F major", "D minor", "Bb major"harmony.chord_progression — set a Roman-numeral progression, e.g. "I IV V I", "ii V I", "I V vi IV"harmony.set_bars — declare per-bar chord changes as concrete chord symbols: "1:Cm7 2:F7 3:Bbmaj7 4:Eb"harmony.harmonize — generate a chord-root voice from the current key + progression (target_voice, optional octave)harmony.walking_bass — generate a walking bass line over chords; adapts to time signature: 4/4 = root-fifth-third-approach, 3/4 = root-fifth-fifth, 6/8 = root-fifth (dotted-quarters), 2/4 = root-approach. Uses harmony.set_bars if set, else falls back to progression. Optional: velocity (ppp–fff, default mf), approach (chromatic [default, 1–2 semitones below], diatonic [scale step below], none [use chord root])harmony.comp — generate a comping (chord accompaniment) voice; adapts to time signature. Style options: quarter_stabs (default), on_beat, eighth_pump, shell_voicings, charleston (4/4 only). Optional: velocity (ppp–fff, default mf)harmony.suggest_harmony — suggest chord harmonizations measure-by-measure for a given voice (advisory)harmony.detect_key — Advanced: run pitch-class analysis on a voice and report the most likely keyharmony.diatonic_transpose — transpose a voice by N diatonic scale steps within the current keydrums.preset — load a named drum pattern for N bars; creates drums_kick, drums_snare, etc. voices on channel 9
house_4on4 — four-on-the-floor kick every beat + clap on 2 & 4 + closed 8th hi-hats; the EDM/dance foundation. Use at 120–130 BPM.rock_8th — driving 8th hi-hat, snare on 2 & 4, kick on 1 & 3; heavier and faster than rock_basic. Use at 130–180 BPM.rock_basic — standard rock backbeat: quarter hi-hat, snare on 2 & 4, kick on 1 & 3; backbone of rock and pop-rock. Use at 100–160 BPM.swing — jazz ride cymbal pattern, hi-hat on 2 & 4, snare on 2 & 4; pair with score.set_swing "2/3" for authentic jazz feel. Use at 120–220 BPM.waltz — simple 3/4: kick on beat 1, snare on beats 2 & 3; works for classical, folk, or pop waltzes. Use at 100–160 BPM.waltz_jazz (3/4) — kick + hi-hat on beat 1, soft brushed snare (MP) on beats 2 & 3; more idiomatic than waltz for jazz waltz contexts. Pair with score.set_swing "2/3".bossa_nova — defining rhythm is the tresillo clave (3+3+2 eighths, i.e., dq+dq+q); creates drums_kick, drums_rim, drums_hihat (eighth hi-hat), drums_clave. Do NOT add swing — the clave replaces swing feel.afrohouse — syncopated (not 4-on-the-floor) kick + open hi-hat on upbeats + hand percussion; creates drums_kick (beat 1, and-of-2, beat 3), drums_clap (2&4), drums_hihat (8ths + open on upbeats), drums_congas (hi/low alternating), drums_maracas (running eighths, velocity P). After loading: set drums_maracas to p or pp and drums_congas to mp.rules.check — run voice-leading and meter rules; percussion voices (channel 9) are automatically skippedrules.check_range — check all notes in a voice against a named instrument's written rangeinstrument.info — get written range, comfortable range, MIDI program, clef, and articulations for a named instrumentform.create_section — capture the current voices (or a subset) as a named section. measures is optional — inferred from the longest voice if omitted; a warning is added if explicit measures differs from the inferred count.form.repeat_section — append a repeat of a previously defined section (optionally with a new label)form.set_ending — attach a 1st/2nd volta ending to a section: section (the repeated section), pass (1 or 2), ending_section (a separately created section with the alternate tail bars). LilyPond renders \repeat volta + \alternative blocks; MIDI plays the correct ending per pass.form.build — assemble sections into a full score; replaces per-section voices with the full assembled versionsform.describe — show the current formal plan (e.g. "A(8) → B(8) → A(8), total: 24 measures")export.all — preferred — creates a folder with .mid, .ly, .json, and PDF (if LilyPond installed). The server auto-prepends a sequential number to the folder name (e.g. folder="sunlit_yard" → 25_sunlit_yard). Do NOT include a number yourself — it will double-prefix (e.g. 25_25_sunlit_yard).export.midi — write a .mid file to the current directoryexport.lilypond — write a .ly file (and engrave PDF if LilyPond is installed)export.musicxml — write a MusicXML 4.0 file (.musicxml). Opens in MuseScore, Dorico, Sibelius, Finale, and most DAWs.score.save — save the full composition state to a JSON snapshot under generated_tracks/ (voices, motifs, metadata, key, swing, bar chords, tempo changes). Use to checkpoint work in progress.score.load — restore a previously saved snapshot, replacing all current state.score.load_midi — import a MIDI file as voices (voice-0, voice-1, …) and set tempo from the file. Existing voices are preserved; call score.clear first for a clean slate. Black keys come back as sharps — re-spell with transform.transpose if needed. path is absolute or relative to the server working directory.score.load_abc — parse an ABC notation string into one or more voices. Headers T: (title), L: (default note length), M: (meter), Q: (tempo), K: (key) are all read. Multi-voice files (V: body headers) produce one voice per V: section, named by the voice ID (e.g. V:soprano → voice soprano, V:1 → voice 1). Single-voice files produce one voice named after the T: field (lowercased, spaces → underscores). Key-signature accidentals apply automatically and persist within each measure; explicit accidentals (^, _, =) override for the remainder of the bar. Octave markers ' (raise) and , (lower) are supported. Tied notes (-) are merged into one longer note. Chord events ([CEG]) are imported as simultaneous pitches. Tuplets ((3, (p:q:r) are duration-scaled correctly (e.g. triplet eighth = 1/12 whole). Use to load folk tunes from The Session (thesession.org) or any ABC corpus. Existing voices are preserved; call score.clear first for a clean slate.Keyboards: piano, bright_piano, honky_tonk (detuned upright), electric_piano (Rhodes), rhodes, harpsichord, organ, accordion
Tuned percussion: vibraphone, marimba
Guitar / bass: guitar, electric_guitar, electric_bass, synth_bass
Strings: violin, viola, cello, strings, synth_strings
Choir: choir
Brass / winds: trumpet, trombone, tuba, french_horn, brass, saxophone, clarinet, flute, oboe, bassoon
Synth: synth_lead (sawtooth — classic house/trance lead), synth_pad (warm pad — chord stabs)
Drums: drums — automatically assigned to MIDI channel 9 (GM percussion). Notes in the voice are treated as GM drum sound numbers. For the full note-to-sound map, read skills/music-composition/drum-note-map.md. Common notes: C2 kick, D2 snare, F#2 closed hi-hat, Bb2 open hi-hat, Eb2 clap, Eb3 ride.
1. score.set_metadata — title, tempo, time sig
2. harmony.set_key — optional; required for harmony.* and diatonic_transpose
3. drums.preset — optional; quick drum pattern for N bars
4. voice.create — one call per voice, with full note sequence
voice.append — add more bars if needed
voice.set_dynamics — set volume per voice (f for lead, mp for pads, etc.)
voice.set_articulation — set articulation per voice (staccato for stabs, etc.)
voice.add_expression_curve — add a CC 11 crescendo/decrescendo curve (from_value→to_value over bar range)
5. transform.transpose — derive harmony voices (parallel thirds, octave doublings)
voice.repeat — extend loops to full length
voice.concat — join sections manually if not using form tools
6. harmony.harmonize — generate an accompaniment voice (needs harmony.set_key first)
7. rules.check — validate voice leading and meter (percussion skipped automatically)
8. form.create_section — snapshot current voices as a named section (A, B, etc.)
form.repeat_section — plan repeats (ABA, AABA, etc.)
form.build — assemble sections; voices replaced with full-length assembled versions
9. score.assign_instrument — one call per voice (instrument assignments survive form.build, so either order works)
10. score.describe — sanity check before export
11. export.all — or export.midi / export.lilypond
House track with chord stabs:
harmony.set_key "Eb major"
voice.create "chords" "<Eb3 G3 Bb3>/q r/q <Ab3 C4 Eb4>/q r/q"
voice.set_dynamics "chords" "mp"
voice.set_articulation "chords" "staccato"
score.assign_instrument "chords" "synth_pad"
Walking bass line (manual):
harmony.set_key "F major"
voice.create "bass" "F2/q A2/q C3/q E3/q | D2/q F2/q A2/q C3/q"
voice.set_dynamics "bass" "f"
score.assign_instrument "bass" "electric_bass"
Diatonic harmony in thirds:
harmony.set_key "G major"
transform.transpose "melody" "M3" "up" target_voice="melody_thirds"
# Now melody_thirds is a parallel major-third above melody (chromatic, not diatonic)
# For diatonic thirds use harmony.diatonic_transpose "melody" steps=2
Structural form (ABA):
# Build A section voices, then:
form.create_section "A" measures=8
# Build B section voices (can be completely different), then:
form.create_section "B" measures=8
form.repeat_section "A"
form.build # assembles A(8) + B(8) + A(8) = 24 measures
# After form.build, all voices are replaced with full 24-bar assembled versions
Volta endings (1st/2nd ending brackets):
# Build main A section (7 bars), then create two 1-bar endings:
form.create_section "A" measures=8 # full 8-bar snapshot
# Build "A_end1" voices (1-bar turnaround back to A):
form.create_section "A_end1" measures=1
# Build "A_end2" voices (1-bar final cadence):
form.create_section "A_end2" measures=1
# Attach endings — pass 1 uses A_end1, pass 2 uses A_end2:
form.set_ending section="A" pass=1 ending_section="A_end1"
form.set_ending section="A" pass=2 ending_section="A_end2"
form.repeat_section "A"
form.build # LilyPond: \repeat volta 2 + \alternative; MIDI: correct ending per pass
Multi-section form with different voices per section (AABB, AABA, etc.):
# Each section gets its own voices. The pattern: build → snapshot → delete → rebuild → snapshot.
# harmony.set_bars must be reset per section; it is section-local.
# --- A section ---
harmony.set_key "D major"
harmony.set_bars "1:D 2:G 3:D 4:A 5:D 6:G 7:A 8:D"
voice.create "melody" "..." # 8 bars
harmony.comp target_voice="chords" style="on_beat" octave=3
voice.create "bodhran_bar" "G2/q G2/q G2/q G2/q"
voice.repeat "bodhran_bar" times=8 target_voice="bodhran"
voice.delete "bodhran_bar"
score.assign_instrument "melody" "flute"
score.assign_instrument "chords" "accordion"
score.assign_instrument "bodhran" "drums"
form.create_section "A" measures=8
form.repeat_section "A" # AABB: queue the second A now
# --- Transition: delete only the voices that change; keep shared ones (e.g. bodhran) ---
voice.delete "melody"
voice.delete "chords"
# --- B section ---
harmony.set_bars "1:G 2:D 3:G 4:A 5:G 6:Em 7:A 8:D"
voice.create "melody" "..." # 8 bars of new material
harmony.comp target_voice="chords" style="on_beat" octave=3
score.assign_instrument "melody" "flute"
score.assign_instrument "chords" "accordion"
# bodhran is still in scope — captured in B section too
form.create_section "B" measures=8
form.repeat_section "B" # AABB: queue the second B
form.build # assembles A(8) + A(8) + B(8) + B(8) = 32 bars
# All voices (melody, chords, bodhran) replaced with full 32-bar assembled versions
Key rules: delete only voices that change between sections; shared voices (drums, bass ostinato) stay in scope and are captured in every section automatically. harmony.set_bars is reset per section — form.build offsets and merges them into the final score.
Ritardando on final bars:
# Assume 24-bar piece at 120 BPM — slow to 60 over the last 3 bars:
score.set_tempo_change start_bar=22 end_bar=24 to_bpm=60 curve="exponential"
# exponential feels more natural than linear for a rit.
Canon at the octave:
voice.create "subject" "C4/q D4/q E4/q G4/q E4/q F4/q G4/q C5/q"
voice.pad_to_measure "subject" start_measure=3 target_voice="answer"
transform.transpose "answer" "P8" "down" target_voice="answer_low"
Motivic development (build a piece from a short cell):
# 1. Define a 4-note cell and save it as a motif
voice.create "cell" "C4/q E4/q G4/q B4/q"
motif.save "cell" startNote=0 endNote=4
# 2. Derive transformed variants — each becomes its own voice
voice.from_motif "cell_inv" motif="cell" transform="invert" axis="C4"
voice.from_motif "cell_retro" motif="cell" transform="retrograde"
voice.from_motif "cell_up5" motif="cell" transform="transpose" interval="P5"
# 3. Augment for a slower countermelody (double all durations)
transform.augment "cell" factor="2/1" target_voice="cell_slow"
# 4. Build voices by repeating cells — stagger entry for canon/imitation effect
voice.repeat "cell" times=4 target_voice="subject"
voice.repeat "cell_inv" times=4 target_voice="counter"
voice.pad_to_measure "counter" start_measure=2 # answer enters 1 bar later
# 5. B section uses retrograde or transposed variant as new material
voice.repeat "cell_retro" times=4 target_voice="b_melody"
voice.repeat "cell_up5" times=4 target_voice="b_counter"
# 6. Assemble into form
form.create_section "A" measures=4
# (swap in B voices here)
form.create_section "B" measures=4
form.repeat_section "A"
form.build # A(4) + B(4) + A(4) = 12 bars, all derived from the original cell
# Clean up ALL scratch voices before form.create_section or export
# Any voice still in scope will become a staff in the PDF
voice.delete "cell"
voice.delete "cell_inv"
voice.delete "cell_retro"
voice.delete "cell_up5"
voice.delete "cell_slow"
The key idea: one cell generates all the material. The transforms (invert, retrograde, transpose, augment) are the compositional engine — not just decoration.
For genre-specific scaffolding (Jazz, Bossa Nova, House, Reggae, Blues, Hip-Hop, Afrohouse, Traditional Irish), read skills/music-composition/genre-reference.md.
e eighths — the renderer adds the lilt.harmony.set_bars chords if set, otherwise falls back to harmony.chord_progression. Always set the key before calling walking_bass (needed for approach notes).harmony.set_bars has been called, chord symbols are automatically rendered above the staves as a \new ChordNames staff. No extra step needed; just export after setting bar chords.form.build — call harmony.set_bars separately for each section before calling form.create_section. form.build automatically merges and offsets each section's chord map to the correct absolute bar numbers in the assembled score. You do not need to manually re-number bars across sections.harmony.comp styles: quarter_stabs (beats 2&4 — jazz default), on_beat (all beats — rock/gospel), eighth_pump (8 per bar — funk), shell_voicings (root+7th on 2&4 — sparse jazz), charleston (dotted-quarter+eighth+quarter+rest — classic jazz). Use octave 3 for piano/Rhodes, octave 4 for guitar.~tie) are for notes that span bar lines or durations not expressible as a single value. The tied notes must have the same pitch; MIDI renders them as a single sustained note.harmony.set_bars chord symbols use the same quality syntax as ChordSymbol.parse: Cm7, F7, Ebmaj7, Am7b5, Ddim7. Bare root (e.g. Eb) means major.target_voice on all transforms is optional — omit to get {name}_transposed etc.transform.transpose transposes all pitches in the chord; transform.augment scales the chord's duration. transform.invert does not invert chord pitches — chords pass through unchanged.score.assign_instrument "kick" "drums" forces channel 9 automatically.harmony.set_key must be called before harmony.harmonize, harmony.diatonic_transpose.form.build rest-fills missing voices automatically — if "bass" exists in A but not B, B gets whole-note rests.form.build, voices are replaced in-place — no _form suffix, no stale originals.rules.check is advisory — violations are warnings/suggestions, never blockers. Percussion voices are skipped.harmony.set_key before exporting for correct notation and DAW display.harmony.set_key is set), and section markers (when form.build is used — DAW timeline shows "intro", "verse", "chorus" etc. at the correct bar positions).cc:expr:N events at phrase peaks and valleys rather than only at the start of a voice.voice.add_expression_curve is bar-absolute — bar numbers are relative to the final assembled score, not the section. In a form.build workflow, add curves after form.build using the assembled bar positions (e.g., if section B starts at bar 9, set start_bar=9). Curves added before form.build keep their original bar numbers, which is correct for section A but wrong for a repeated section B.from_value=20 to_value=90 curve=exponential), strings at bar 10, cello at bar 12. The exponential shape (quadratic ease-in: slow start, fast finish) suits crescendos; combine with a second curve going back down for a complete swell arc.