README.md

MusicQuery

A notation-based query language for symbolic music. Try it!

Query language

The query language is inspired by text regular expressions. A search query is expressed as musical notation. The query is encoded in MEI. A query is a subset of a normal score, with some specific query semantics.

Query semantics

A query must be a valid MEI excerpt contains any of the following elements.

<note>

Matches one note. Duration (dur), pitch name (pname), octave (oct) and accidentals (accid) are taken into account.

• Accidentals must always be spelled out (a key signature of C major is assumed).
• query:any-duration="true" matches any accidental, that is - any pitch with the specified note name and octave.
• query:any-pitch="true" matches any pitch, that is, any note with the specified duration.
• query:any-duration="true" matches any duration, that is, any note with the specified pitch.

<query:or>

Indicates an "or" operator (translates to the | regular expression operator). Rendered as a vertical line on the staff.

<query:group>

Used for grouping and quantifying. Corresponds to parentheses and quantifiers in regular expression. Can contain any other query element, including nested <query:group>s.

Attributes min-occurrences and max-occurrences specify how many occurrences the group will match. For now only values that map to regular expression quantifiers * (zero or more), + (one or more), and ? (zero or one) are supported.

Set bracket.visible="false" if you wish to hide a group's bracket.

<space>

Ignored. Can be used to adjust spacing for nicer rendering. Example:

<space dur="8" />

<beam>

Ignored. Can be used to adjust beaming for nicer rendering. Can contain <note> elements. Example:

<beam>
    <note pname="c" oct="5" dur="8" dots="1" accid="s"/>
    <note pname="d" oct="5" dur="16" />
    <note pname="c" oct="5" dur="8" accid="s"/>
</beam>

Algorithm

The query is translated behind the scenes to a regular expression and executed on a score that is encoded in the Humdrum ****kern representation.

The regular expression itself is complicated. It is possible to hand craft an expression, but it is error prone. For example, the following easy to read music query:

<note dur="8" dots="1" query:duration-only="true" />
<note dur="16" query:duration-only="true" />
<note dur="8" query:duration-only="true" />
<query:group min-occurrences="0" max-occurrences="1" bracket.visible="false">
    <note pname="e" oct="5" dur="4" />
</query:group>

is translated to the following monstrous regular expression:

(^|\t)(&?{)?(&?\()?\[?8\.([a-g]+|[A-G]+)(#+|-+|n)?(?![a-gA-G#\-n]).*
(^[!.*=].*
)*?(^|\t)(&?{)?(&?\()?\[?16([a-g]+|[A-G]+)(#+|-+|n)?(?![a-gA-G#\-n]).*
(^[!.*=].*
)*?(^|\t)(&?{)?(&?\()?\[?8([a-g]+|[A-G]+)(#+|-+|n)?(?![a-gA-G#\-n]).*
(^[!.*=].*
)*?((^|\t)(&?{)?(&?\()?\[?4ee(?![a-gA-G#\-n]).*
(^[!.*=].*
)*?)?

Rendering

The query and score are rendered to SVG in the browser using Verovio. Verovio supports both MEI (for the query) and Humdrum (for the score). Search results are highlighted in the score using a Humdrum marker that is added to matched lines.

Since Verovio doesn't support all the features needed to render a query, some extra patches are added to the rendered SVG after Verovio renders it.

Future work

This project is a proof-of-concept. A lot of work has been done previously on symbolic music searching, but I have not encountered a graphical music query language. The target audience of this language is musicologists, however, in its current state the language is of limited use to them. The following should be implemented.

• Polyphonic music support. Regular expressions are powerful enough to support polyphonic music searching in the Humdrum format. However, the semantics of the query language are hard to define. I would like to explore two approaches:

  1. Preprocess a two-voice Humdrum score using hint and mint (harmonic and melodic intervals), and define query operators which operate on that. (Scores with more than two voices can be processed in pairs of voices.)
  2. Use a constraint-based system based on Structured Polyphonic Patterns (by Mathieu Bergeron). Define graphical query operators that translate to that language and implement the search engine.

• The query language itself should be extended to support:

  • Chords.
  • Additional "layers" of searching: e.g., harmony, dynamics, articulation, which can be added as constraints. (E.g., find an A only on subdominant or dominant chords.)
  • Chroma and pitch class (octave invariance).
  • Transposition invariance (melodic intervals).
  • 'Any note' (any pitch and any rhythm).
  • Rests (including wildcards - "any rest").

• Users should be able to input a query using a graphical interface. The interface could be based on Vida.js or nCoda (both are open source projects with a web-based notation editor).

• Rendering should be improved. Right now, Verovio is used in a patchy way because it doesn't support all the needed rendering features.

  • Support for rhythmic notation (instead of tenuto). This will be possible when Verovio supports custom noteheads (head.shape, see PR).
  • A custom 'OR' symbol (dashed vertical line) should be rendered.
  • A bracket object supporting arbitrary text should be added. It should be similar to a slur object rather than a tuplet, but look like a tuplet.

• Rigorous tests should be added.