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🎼 A sheet music to polylines renderer

Samples | Online Editor | API | Syntax

In goes a midi file or a simple markup format, and out comes ✨polylines✨, which can then be used for animation, plotting and various procedural drawing fun.

🚧 This project is a work in progress and currently supports a subset of sheet music notation. Errors and ugliness might occur from time to time*. For professional quality scorewriting, check out instead. 🚧


  • Supports most everyday classical music symbols;
  • Exports polylines, svg, pdf, gif, midi and more;
  • Lightweight: < 150KB minified; No dependencies;
  • Uses Hershey Fonts for text and symbols; You can load custom hershey fonts for rendering unicode etc;
  • Includes basic animation and handdrawn effects generator;
  • Use as browser/node.js library or commandline interface.

For examples, below are the first couple measures of Grieg's "Solitary Wanderer", typeset in legumes, with regular, animated and hand-drawn styles:

You can find at the bottom of this document the full score, or better yet, Checkout the samples folder for a more comprehensive showcase featuring music by various composers!

*legumes is an acronym for Lingdong's Erratic and Generally Useless Musical Engraving System.


The easiest way to try out the project is by using the Online Editor, which supports syntax highlighting and midi playback. For more advanced usage, there're commandline and programming interfaces, described below:


The legc executable included in the repo is a shebang'ed node.js script. You can easily invoke it in the commandline via ./legc (or legc if placed/aliased in PATH) if you have node.js installed.

Minimal example, rendering a score to SVG:

legc --format svg samples/minuet_G.txt > output.svg

Another example, render a score to an animated svg, specifying some rendering options:

legc --format svg-anim \
  --stem-length 3 --title-text-size 28 --page-margin-x 120\
  samples/minuet_G.txt > output.svg

The commandline tool supports some 50+ rendering/export options, view the full list by typing:

legc --help


Built JavaScript files acn be found in dist/ folder. Import them via

<script src="dist/legumes.min.js"></script>


const legumes = require("dist/legumes");

You can find the full API doc here, but here's a minimal example:

const txt = fs.readFileSync("samples/minuet_G.txt").toString();

// build a score from the text-based markup
const score = legumes.parse_txt(txt);

// compile the score to pre-compute properties for drawing

// draw the score
let drawing = legumes.render_score(score);

// export drawing to SVG format
let svg = legumes.export_svg(drawing)

// document.body.innerHTML = svg;

You can configure rendering options via the CONFIG object, e.g. :

legumes.CONFIG.LYRIC_SCALE = 0.8;

Midi files can also be rendered, but note that midi is not a suitable format storing sheet music, and educated guesses has to be made converting it to one:

let bytes_in = Array.from(new Uint8Array(fs.readFileSync("input.mid")));
let midi_file = legumes.parse_midi(bytes_in);
let score = legumes.score_from_midi(midi_file);
fs.writeFileSync("output.svg", legumes.export_svg(drawing));

What one could do, is read a midi file, and export it as markup text, make improvements by hand, and render the latter instead:

let bytes_in = Array.from(new Uint8Array(fs.readFileSync("input.mid")));
let midi_file = legumes.parse_midi(bytes_in);
let score = legumes.score_from_midi(midi_file);
let txt = legumes.export_txt(score);
fs.writeFileSync("score.txt", txt);

In addition to the supported input file formats, you can construct your own score object to feed into legumes, as long as it conforms to the interface:

interface Score_itf{
  title:       string[];
  composer:    string[];
  tempo?:      Tempo_itf;
  instruments: Instrument_group_itf[];
  slurs:       Slur_itf[];
  measures:    Measure_itf[];
  crescs:      Cresc_itf[];

You can find more details about these interfaces in API doc and src/common.ts.

legumes render with several stages. You can unplug the final polylines output and write a custom renderer that interprets the computed element layout. For example, visualize the elements with export_mock_svg routine:

let drawing = legumes.render_score(score,{compute_polylines:false});
let svg = legumes.export_mock_svg(drawing)

More details can be found in src/drawing.ts.

Special thanks to my friend @jiangzoi (Computational music major at CMU) and my mother (piano teacher) for advice and help on sheet music, of which I came to realize I know little as I progress with the project.

Issues & Pull request are welcome.