leetsheet

leadsheet

This package contains the Sheet module which can be used to handle musical leadsheets (and other control flows) in json and text format.

• Snippet: text format, usable for quick and easy input and storage of sheets
• Sheet/Measure: JSON Format, usable for parsing / rendering / playing sheets
• RealParser: Parses ireal pro format => access to thousands of songs
• TBD: abc parser
• TBD: musicXML parser

Design Goals

• Keep it functional: inputs and outputs can be transformed using function chaining
• Keep it immutable: arrays/objects never change
• Keep it static: no class instances => outputs are primitives, objects or arrays
• strictly typed: typescript first
• Influenced by Tonal, Tidal Cycles and Impro-Visor

Demo

You can run the demo via npm run demo

Snippets

A Snippet is a textual representation of a leadsheet.

Example

const snippet = `
|: E-7b5    | A7b9      | D-     | %          |
|  G-7      | C7        | F^7    | E-7b5 A7b9 |
|1 D-       | G-7       | Bb7    | A7b9       |
|  D-       | G7#11     | E-7b5  | A7b9      :|
|2 D-       | G-7       | Bb7    | A7b9       |
|  D- B7    | Bb7#11 A7 | D-     | %          |
`;

• Measures are seperated by "|"

• The measure body is seperated by spaces

• ":" signs repeat a section

• 1/2.. represent houses

• actual content is arbitrary

  • could be chords or melody or anything
  • the example uses ireal style chords
  • parsing is done by tonal in the jazzband package

All Supported Signs

• (DC)
• (DS) with (Segno) or (S)
• (Fine) or (Fi)
• (ToCoda) or (2Q)
• (Coda) or (Q)
• see Snippet.test for more examples
• implemented according to formal semantics for music notation control flow page 6

Snippet.expand

Snippet.expand(snippet);

yields

|  E-7b5   | A7b9      | D-     | %          |
|  G-7     | C7        | F^7    | E-7b5 A7b9 |
|  D-      | G-7       | Bb7    | A7b9       |
|  D-      | G7#11     | E-7b5  | A7b9       |
|  E-7b5   | A7b9      | D-     | %          |
|  G-7     | C7        | F^7    | E-7b5 A7b9 |
|  D-      | G-7       | Bb7    | A7b9       |
|  D- B7   | Bb7#11 A7 | D-     | %          |

Snippet.minify (uglify)

Uglifies a snippet to a compact string:

Snippet.minify(
  `
      |: E-7b5    | A7b9      | D-     | x          |
      |  G-7      | C7        | F^7    | E-7b5 A7b9 |
      |1 D-       | G-7       | Bb7    | A7b9       |
      |  D-       | G7#11     | E-7b5  | A7b9      :|
      |2 D-       | G-7       | Bb7    | A7b9       |
      |  D- B7    | Bb7#11 A7 | D-     | x          |
      `,
  true // => url safe flag
);

yields

RE-7b5IA7b9ID-IxIG-7IC7IFM7IE-7b5_A7b9I1_D-IG-7IBb7IA7b9ID-IG7Y11IE-7b5IA7b9RI2_D-IG-7IBb7IA7b9ID-_B7IBb7Y11_A7ID-Ix

This string only contains url safe chars and has no information loss. Without using the flag, the minifed version looks like this:

:E-7b5|A7b9|D-|x|G-7|C7|F^7|E-7b5 A7b9|1 D-|G-7|Bb7|A7b9|D-|G7#11|E-7b5|A7b9:|2 D-|G-7|Bb7|A7b9|D- B7|Bb7#11 A7|D-|x

Snippet.format (beautify)

Beautifies a snippet to 4 cells per line with equal spacing. Works both with url safe and non url safe snippets:

Snippet.format(
  'RE-7b5IA7b9ID-IxIG-7IC7IFM7IE-7b5_A7b9I1_D-IG-7IBb7IA7b9ID-IG7Y11IE-7b5IA7b9RI2_D-IG-7IBb7IA7b9ID-_B7IBb7Y11_A7ID-Ix'
);
// or
Snippet.format(
  ':E-7b5|A7b9|D-|x|G-7|C7|F^7|E-7b5 A7b9|1 D-|G-7|Bb7|A7b9|D-|G7#11|E-7b5|A7b9:|2 D-|G-7|Bb7|A7b9|D- B7|Bb7#11 A7|D-|x'
);

both yield

|: E-7b5    | A7b9      | D-     | x          |
|  G-7      | C7        | F^7    | E-7b5 A7b9 |
|1 D-       | G-7       | Bb7    | A7b9       |
|  D-       | G7#11     | E-7b5  | A7b9      :|
|2 D-       | G-7       | Bb7    | A7b9       |
|  D- B7    | Bb7#11 A7 | D-     | x          |

• no information is lost

Snippet.parse

Converts a text snippet to JSON which is typed Measure<string>[]

Snippet.parse('D-7 G7 | C^7');

yields

[['D-7', 'G7'], 'C^7'];

• note that the first bar is an array

When using signs:

const parsed = Snippet.parse(`
|: C7  | F7 |1 C7 | C7 :|
            |2 C7 | C7  |
| F7   | F7 |  C7 | A7  |
| D-7  | G7 |  C7 | G7  |
`);

yields

[
  { body: ['C7'], signs: ['{'] },
  'F7',
  { house: 1, body: ['C7'] },
  { body: ['C7'], signs: ['}'] },
  { house: 2, body: ['C7'] },
  'C7',
  'F7',
  'F7',
  'C7',
  'A7',
  'D-7',
  'G7',
  'C7',
  'G7'
];

All measures without signs remain strings. If you want the format unified, you can use Measure.from:

parsed.map(measure => Measure.from(measure));

yields

[
  { "signs": ["{"], "body": ["C7"] },
  { "body": ["F7"] },
  { "house": 1, "body": ["C7"] },
  { "signs": ["}"], "body": ["C7"] },
  { "house": 2, "body": ["C7"] },
  { "body": ["C7"] },
  { "body": ["F7"] },
  { "body": ["F7"] },
  { "body": ["C7"] },
  { "body": ["A7"] },
  { "body": ["D-7"] },
  { "body": ["G7"] },
  { "body": ["C7"] },
  { "body": ["G7"] }
]

This brings us seamlessly to the Measure Format:

Measures

A Measure is an object representing one measure of a leadsheet.

Properties:

• body: contains any value
• signs: control signs like "{" or "DC"
• house: house number
• times: number of repeats (not supported by snippet yet)
• section: section name (not supported by snippet yet)
• See Measure.ts for all possible properties.

To render multiple Measures, you can use the Sheet namespace:

Sheet.render()

Resolves all control signs/repeats/houses and outputs the rendered measures typed as RenderedMeasure<string>[]. The array elements can either be of type Measure or just primitives:

Simple example:

const measures = ['A', 'B', { body: ['C'], signs: ['Coda'] }];
// equals this snippet: "| A | B | (Coda) C |"
Sheet.render(measures, { forms: 3 });

generates

[
  { body: ['A'], form: 0, index: 0, totalForms: 3 },
  { body: ['B'], form: 0, index: 1, totalForms: 3 },
  { body: ['A'], form: 1, index: 0, totalForms: 3 },
  { body: ['B'], form: 1, index: 1, totalForms: 3 },
  { body: ['A'], form: 2, index: 0, totalForms: 3 },
  { body: ['B'], form: 2, index: 1, totalForms: 3 },
  { body: ['C'], form: 2, index: 2, totalForms: 3 }
];

As you see, the measures are repeated three times due to the forms option. The last form jumps into the coda.

• body: content of measure
• form: current form
• index: original measure index
• total number of forms rendered

Side Note: Although you can use short signs like "(Q)" in a snippet, a measure will only accept "Coda" (see Snippet>controlSigns).