musicxml-io

TypeScript library for parsing and serializing MusicXML.

Architecture

┌─────────────────┐      ┌─────────────────┐      ┌─────────────────┐
│   MusicXML      │      │                 │      │   MusicXML      │
│   .xml / .mxl   │─────▶│      Score      │─────▶│   .xml / .mxl   │
└─────────────────┘      │                 │      └─────────────────┘
                   parse │   ┌─────────┐   │ serialize
                         │   │ parts   │   │      ┌─────────────────┐
                         │   │  └─measures │      │     MIDI        │
                         │   │    └─entries│─────▶│   .mid          │
                         │   └─────────┘   │      └─────────────────┘
                         │                 │ exportMidi
                         └────────┬────────┘
                                  │
              ┌───────────────────┼───────────────────┐
              │                   │                   │
              ▼                   ▼                   ▼
     ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
     │ QUERIES         │ │ OPERATIONS      │ │ ACCESSORS       │
     │                 │ │                 │ │                 │
     │ Score-level     │ │ Score mutation  │ │ Entry-level     │
     │ read operations │ │ operations      │ │ helpers         │
     │                 │ │                 │ │                 │
     │ getMeasure()    │ │ transpose()     │ │ isRest()        │
     │ findNotes()     │ │ addNote()       │ │ isPitchedNote() │
     │ getAllNotes()   │ │ changeKey()     │ │ getPartName()   │
     │ getHarmonies()  │ │ insertMeasure() │ │ hasTie()        │
     └─────────────────┘ └─────────────────┘ └─────────────────┘
                                  │
                                  ▼
                         ┌─────────────────┐
                         │ VALIDATE        │
                         │                 │
                         │ validate()      │
                         │ isValid()       │
                         │ assertValid()   │
                         └─────────────────┘

Module Structure

| Module | File | Description | |--------|------|-------------| | Query | src/query/index.ts | Score-level read operations (get, find, iterate) | | Operations | src/operations/index.ts | Score mutation operations (add, delete, modify) | | Accessors | src/entry-accessors.ts | Entry-level helpers for notes, directions, parts |

Install

npm install musicxml-io

Usage

import { parse, serialize, transpose } from 'musicxml-io';

const score = parse(xmlString);
const transposed = transpose(score, 2);  // up 2 semitones
const output = serialize(transposed);

⚠️ Warning: This library's API is not yet stable and may change between versions.

File I/O (Node.js)

import { parseFile, serializeToFile } from 'musicxml-io';

const score = await parseFile('input.mxl');
await serializeToFile(score, 'output.xml');

Operations

import { addNote, changeKey, changeTime } from 'musicxml-io';

const updated = addNote(score, {
  partIndex: 0,
  measureNumber: 1,
  pitch: { step: 'C', octave: 4 },
  duration: 4,
  type: 'quarter',
});

const inG = changeKey(score, { fifths: 1 }, 0, 1);
const waltz = changeTime(score, { beats: 3, beatType: 4 }, 0, 1);

Query

import { findNotes, getAllNotes, getMeasureCount, getHarmonies } from 'musicxml-io';

const notes = getAllNotes(score);
const quarterNotes = findNotes(score, { noteType: 'quarter' });
const count = getMeasureCount(score);
const harmonies = getHarmonies(score);  // chord symbols (C7, Dm, etc.)

Accessors

Entry-level helpers for working with individual notes, directions, and parts:

import {
  getAllNotes,
  isRest, isPitchedNote, hasTie, isChordNote,
  getPartName,
  getDirectionOfKind, getSoundTempo
} from 'musicxml-io';

// NoteEntry helpers
for (const item of getAllNotes(score)) {
  if (isRest(item.note)) continue;
  if (isPitchedNote(item.note)) {
    console.log(`${item.note.pitch!.step}${item.note.pitch!.octave}`);
  }
  if (hasTie(item.note)) console.log('Tied note');
  if (isChordNote(item.note)) console.log('Part of chord');
}

// PartInfo helpers
const partName = getPartName(score, 'P1'); // 'Piano'

// DirectionEntry helpers
for (const entry of measure.entries) {
  if (entry.type === 'direction') {
    const dynamics = getDirectionOfKind(entry, 'dynamics');
    if (dynamics) console.log(dynamics.value); // 'ff', 'pp', etc.

    const tempo = getSoundTempo(entry);
    if (tempo) console.log(`Tempo: ${tempo} BPM`);
  }
}

MIDI Export

import { exportMidi } from 'musicxml-io';

const midi = exportMidi(score, { tempo: 120 });

Validation

import { validate, isValid } from 'musicxml-io';

const { valid, errors } = validate(score);

API

Parse / Serialize

| Function | Description | |----------|-------------| | parse(xml) | Parse MusicXML string | | parseFile(path) | Parse from file | | parseCompressed(buffer) | Parse .mxl | | parseAuto(data) | Auto-detect format | | serialize(score) | To MusicXML string | | serializeToFile(score, path) | To file | | serializeCompressed(score) | To .mxl | | exportMidi(score) | To MIDI |

Operations

| Function | Description | |----------|-------------| | transpose(score, semitones) | Transpose pitches | | insertNote(score, options) | Insert note at position | | removeNote(score, options) | Remove note (replace with rest) | | addChord(score, options) | Add note to chord | | setNotePitch(score, options) | Change note pitch | | changeNoteDuration(score, options) | Change note duration | | addVoice(score, options) | Add voice to measure | | addPart(score, options) | Add part to score | | removePart(score, options) | Remove part from score | | setStaves(score, options) | Set staff count | | changeKey(score, key, part, measure) | Change key signature | | changeTime(score, time, part, measure) | Change time signature | | insertMeasure(score, part, after) | Insert measure | | deleteMeasure(score, part, measure) | Delete measure | | addTie(score, options) | Add tie between notes | | addSlur(score, options) | Add slur between notes | | addArticulation(score, options) | Add staccato, accent, etc. | | addDynamics(score, options) | Add dynamics (f, p, etc.) | | modifyDynamics(score, options) | Modify dynamics | | addTempo(score, options) | Add tempo marking | | modifyTempo(score, options) | Modify tempo | | addOrnament(score, options) | Add trill, turn, etc. | | addText(score, options) | Add text direction | | addLyric(score, options) | Add lyric to note | | autoBeam(score, options) | Auto-beam notes | | createTuplet(score, options) | Create tuplet | | addChordSymbol(score, options) | Add chord symbol | | changeClef(score, options) | Change clef | | setBarline(score, options) | Change barline style | | addRepeat(score, options) | Add repeat barline | | addEnding(score, options) | Add first/second ending | | addFermata(score, options) | Add fermata | | addWedge(score, options) | Add crescendo/diminuendo | | addPedal(score, options) | Add pedal marking | | addGraceNote(score, options) | Add grace note |

See OPERATIONS.md for the complete list.

Query

| Function | Description | |----------|-------------| | getAllNotes(score) | All notes with context | | findNotes(score, filter) | Filter notes by criteria | | getMeasure(score, { part, measure }) | Get measure by number | | getMeasureByIndex(score, { part, measureIndex }) | Get measure by index | | getMeasureCount(score) | Total measure count | | getChords(measure) | Chord groups in measure | | countNotes(score) | Total note count | | getHarmonies(score) | All chord symbols | | getDynamics(score) | All dynamics markings | | getTempoMarkings(score) | All tempo markings |

Accessors

Entry-level helpers for individual notes, directions, and parts.

NoteEntry

| Function | Description | |----------|-------------| | isRest(note) | Check if rest | | isPitchedNote(note) | Check if has pitch | | isUnpitchedNote(note) | Check if percussion | | isChordNote(note) | Check if part of chord | | isGraceNote(note) | Check if grace note | | isCueNote(note) | Check if cue note | | hasTie(note) | Check if tied | | hasTieStart(note) | Check if tie starts | | hasTieStop(note) | Check if tie stops | | hasBeam(note) | Check if beamed | | hasLyrics(note) | Check if has lyrics | | hasNotations(note) | Check if has notations | | hasTuplet(note) | Check if in tuplet |

DirectionEntry

| Function | Description | |----------|-------------| | getDirectionOfKind(entry, kind) | Get first direction type | | getDirectionsOfKind(entry, kind) | Get all direction types | | hasDirectionOfKind(entry, kind) | Check if has type | | getSoundTempo(entry) | Get tempo from sound | | getSoundDynamics(entry) | Get dynamics (0-127) | | getSoundDamperPedal(entry) | Get damper pedal state | | getSoundSoftPedal(entry) | Get soft pedal state | | getSoundSostenutoPedal(entry) | Get sostenuto pedal state |

PartInfo

| Function | Description | |----------|-------------| | getPartInfo(score, id) | Get part info by ID | | getPartName(score, id) | Get part name | | getPartAbbreviation(score, id) | Get part abbreviation | | getAllPartInfos(score) | Get all part infos | | getPartNameMap(score) | Get ID to name map | | isPartInfo(entry) | Type guard for PartInfo |

Validate

| Function | Description | |----------|-------------| | validate(score) | Validation errors | | isValid(score) | Boolean check | | assertValid(score) | Throw if invalid |

Tree-shaking

import { transpose } from 'musicxml-io/operations';
import { findNotes } from 'musicxml-io/query';
import { isRest, getPartName } from 'musicxml-io/entry-accessors';

Unique Element IDs

All elements in the Score structure have a unique _id property that is automatically generated when:

• MusicXML is parsed/imported
• New elements are created via operations

The ID format is "i" + nanoid(10) (11 characters total), where:

• "i" prefix ensures XML ID compatibility (IDs must start with a letter or underscore)
• nanoid(10) generates a URL-safe unique identifier

import { parse, generateId } from 'musicxml-io';

const score = parse(xmlString);
console.log(score._id);           // e.g., "iV1StGXR8_Z"
console.log(score.parts[0]._id);  // e.g., "i2x4K9mL1Qp"

// Generate IDs manually for custom elements
const customId = generateId();    // e.g., "iAb3Cd5Ef7H"

This feature enables:

• Tracking elements across transformations
• Building element references in external systems
• Implementing undo/redo functionality
• Diffing and merging scores

Round-trip Fidelity

| Metric | Score | |--------|------:| | Overall | 99.6% | | Node coverage | 99.9% | | Attribute coverage | 95.9% |

License

MIT