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What is music21?

Music21 is a set of tools for helping scholars and other active listeners answer questions about music quickly and simply. If you’ve ever asked yourself a question like, “I wonder how often Bach does that” or “I wish I knew which band was the first to use these chords in this order,” or “I’ll bet we’d know more about Renaissance counterpoint (or Indian ragas or post-tonal pitch structures or the form of minuets) if I could write a program to automatically write more of them,” then music21 can help you with your work.

How simple is music21 to use?

Extremely. After starting Python and typing "from music21 import *" you can do all of these things with only a single line of music21 code:

Display a short melody in musical notation:
converter.parse("tinynotation: 3/4 c4 d8 f g16 a g f#").show()

Print the twelve-tone matrix for a tone row (in this case the opening of Schoenberg's Fourth String Quartet):
print (serial.rowToMatrix([2,1,9,10,5,3,4,0,8,7,6,11]) )

or since all the 2nd-Viennese school rows are already available as objects, you can type:
print (serial.getHistoricalRowByName('RowSchoenbergOp37').matrix() )

Convert a file from Humdrum's **kern data format to MusicXML for editing in Finale or Sibelius:
converter.parse('/users/cuthbert/docs/composition.krn').write('musicxml')

With five lines of music21 code or less, you can:

Prepare a thematic (incipit) catalog of every Bach chorale that is in 3/4:

catalog = stream.Opus()
for workName in corpus.chorales.Iterator():
  work = converter.parse(workName)
  firstTS = work.recurse().getElementsByClass('TimeSignature')[0]
  if firstTS.ratioString == '6/8':
    catalog.append(work.measures(0, 2))
catalog.show()

Google every motet in your database that includes the word ‘exultavit’ in the superius (soprano) part (even if broken up as multiple syllables in the source file) to see how common the motet's text is (assuming you have a bunch of motets in "listOfMotets"):

import webbrowser
for motet in listOfMotets:
  superius = motet[0]
  lyrics = text.assembleLyrics(part)
  if 'exultavit' in lyrics:
    webbrowser.open('http://www.google.com/search?&q=' + lyrics)

Add the German name (i.e., B♭ = B, B = H, A♯ = Ais) under each note of a Bach chorale and show the new score:

bwv295 = corpus.parse('bach/bwv295')
for thisNote in bwv295.recurse().notes:
  thisNote.addLyric(thisNote.pitch.german)
bwv295.show()

Of course, you are never limited to just using five lines to do tasks with music21. In the demos folder of the music21 package and in the sample problems page (and throughout the documentation) you’ll find examples of more complicated problems that music21 is well-suited to solving, such as cataloging the rhythms of a piece from most to least-frequently used.

Music21 builds on preexisting frameworks and technologies such as Humdrum, MusicXML, MuseData, MIDI, and Lilypond but music21 uses an object-oriented skeleton that makes it easier to handle complex data. But at the same time music21 tries to keep its code clear and make reusing existing code simple. With music21 once you (or anyone else) has written a program to solve a problem, that program can easily become a module to be adapted or built upon to solve dozens of similar (but not identical) problems.

Interested in learning more?

Latest music21 News

[October 29, 2018 11:08 am] « » [music21]
Version 5.5 brings some small but important improvements to music21 and is a maintenance release. V5.5 is the first release to no longer support Python 3.4, so please use Python 3.5 or higher to upgrade.
Important changes and bugfixes.
  1. Chord.commonName gets many improvements, detecting for instance, the differences between dominant-seventh chords and augmented sixths.
  2. much better metadata on Bach Chorals (thanks Norman!)
  3. Stream.voiceToParts() is much improved and gets an optional separateById keyword argument which will only merge voices whose .id matches. -- this is very exciting to me from an analytical perspective and one reason I decided to release now.
  4. Volpiano is upgraded to a full conversion method. Most people will go, "buh??" people who work with Gregorian chant will rejoice.
  5. obj.activeSite is set more reliably.
  6. better error messages if a stream cannot be chordified.
  7. ABC parses all major and minor keys properly -- there were a few bugs especially on sharp keys in minor before. (Thanks @a-papadopoulos )
  8. "Cad64" is now an acceptable RomanNumeral alternative for "I64" for all you theorists out there who cringed when writing it. Resolves to I64 in major context (or as a secondary dominant) and i64 in minor contexts.
  9. bug fixes on rounding approximate durations (such as in MIDI parsing)
  10. converter.parse('tinyNotation: ...', raiseExceptions=True) allows tinyNotation to bubble up anything that prevents reading a token. off by default, but useful for debugging. Expect this keyword to start appearing (w/ default False) for other conversion methods.
  11. Changed: as promised years ago, the default on Stream.recurse() is now NOT to include the caller itself in recursion. Use keyword argument "includeSelf=True" to do so. Recurse keywords are keyword only.
  12. Changed: arguments to Music21Object.contextSites are keyword only. This fixes a few little bugs. Same with Stream.elementsChanged()
  13. MusicXML stores Fingerings properly (thanks @hofst !)
  14. Fixes for extreme pitchbends (very close to wheel minimum) on MIDI.
  15. Dropped bug-fixes for very old versions of Sibelius and MuseScore < 2.0
  16. Added bug catching for MusicXML that gives the shape of the clef ('G', 'F') but no line -- uses sensible defaults. And many other cases in MusicXML where an attribute is empty (as one musicxml writer is now producing)
As always thanks to MIT, the Seaver Institute, and the NEH for funding early development of music21.

Upgrade with “pip install --upgrade music21”
[August 12, 2018 19:03 pm] « » [music21]
[March 17, 2018 17:11 pm] « » [music21]
music21 v.5 is PYTHON 3 ONLY
Do not upgrade to this version if you are using Python 2.7 (or better still, upgrade yourself to Python 3.6 instead). It runs on Python 3.4-3.6 only.  music21 v.4 is the last version to support Python 2.
run "pip3 install music21" to install.
music21 v.5 brings with it seven months of determined work by an open-source team to streamline music analysis. The move to Python 3 allowed us to greatly simplify the codebase and to speed up many commonly used features in music21. If you are apprehensive about switching to Python 3, I hope you'll be convinced that it is worth it the first time you run chordify() on a large score v.5. and see that what might have taken an hour can now be done in few seconds. A great number of bugs involving working with non-English text have been fixed.
As a new major release, music21 breaks backwards compatibility where necessary and deprecates underused functions and things that can be done better in other ways. We're always trying to balance bringing new features with keeping the software as simple to use as possible.
Major changes:
  • Python 3 only. Yes, I said that but I'm saying it again. This change has made developing much faster and a lot more fun. Also it's made music21 more powerful and faster.
  • Chordify moves from O(n^2) to O(n) time -- Chordify on large scores works great now.
  • MusicXML roundtrip now preserves much about appearance, style, metadata, etc. -- you can now load a musicxml file into music21 and back into your software and 90% of the time you'll get visually the same result as the original software. Finale roundtrip is especially good!
  • Corpora searching is much better and much faster. Metadata is stored in pickle format.
  • Feature Extraction runs multicore by default. Together with the average of 10x faster chordify, feature extraction on large datasets on multicore systems is now very strong. Parallel processing is easier and much better documented.
  • Features with JSymbolic equivalents much more closely match the spec and new features have been added (thanks Micah Walter!)
  • Many routines that used to return string filepaths now return pathlib.Path objects. Especially useful for people running on Python 3.6
  • Almost all functions deprecated in v. 4 have been removed.
  • Many keyword functions now require the keyword, so instead of makeNotation(True), call makeNotation(inPlace=True), since explicit is better than implicit, this is a good way of being sure that only the right arguments are being changed.
  • parsing of Volpiano (Gregorian chant notation) added.
  • RehearsalMarks are now supported internally and in MusicXML reading/writing.
  • Other musicXML improvements: Volume of individual notes is now imported and exported. Glissandi and barlines and transposition work better. More elements can be hidden. Empty spaces in MusicXML measures are converted to hidden rests, to avoid gapped streams. Pitches in chords on musicxml import are always sorted from lowest to highest. Fretboard diagrams are supported and Instrument objects have the MusicXML v. 3 sound tags attached. (thanks to Luke Poeppel for these last two)
  • Corpora improvments: works by Amy Beach, Schubert (Lindebaum), better Bach Chorales (thanks Dr. Norman Schmidt), and Scott Joplin. Errors in various pieces fixed.
  • Scales and IntervalNetworks run much faster and are better documented.
  • voiceLeading.VoiceLeadingQuartet improved. compatibility change: improperResolution renamed to isProperResolution and improved. Former title implied that False meant it was proper; now the title reflects the output. Many other fixes and improvements thanks to Ryaan Ahmed.
  • analysis.transposition -- searches pitch lists for number of distinct transpositions; neoriemannian analysis improvements (thanks to Mark Gotham for both) Stream alignment tools in alpha.analysis (thanks to Emily Zhang)
  • Copyright and other metadata is preserved in many formats on import. This is just being a good neighbor.
  • Demos and most alpha code has been moved to a new separate repository: https://github.com/cuthbertLab/music21-demos -- they will be updated much less frequently. This will also make code development faster. Thanks to all who have contributed to music21's development. We'll be able to get more demos into the codebase by not needing to update them at every moment.
  • Bugs fixed: chords not in voices in measures with voices were not found in some routines. Instrument objects without midiProgram explicitly set get a program on MIDI output. MIDI no longer inserts a rest at the beginning (thanks KKONZ). Chord.normalOrder fixed (thanks luiselroquero), bugs in Capella parsing. Bugs related to Apple File System High Sierra not sorting files by default. Accented braille characters are exported properly.
  • Docs can be downloaded as a separate zip file.
I have no major backward-incompatable plans for the near future, so I expect v.5 to have a longer life than the last few releases (at least 18 months, and possibly 2-3 years), but work will continue on smaller subreleases to come. Thanks again to MIT, School of Humanities, Arts, and Social Sciences, and the Music and Theater Arts section for their support of music21 and the Seaver Institute and the National Endowment for the Humanities for financial support.
[March 10, 2018 17:02 pm] « » [music21]
The first and hopefully only beta/release candidate of music21 v. 5 has been released.    If no bugs are discovered/reported, I expect this to be the release version to be released next weekend and I’m going to hold off on merging any new pull requests until then.   I expect v.5 of music21 to have a longer than usual lifespan (at least 18 months, possibly more) and don’t have any backwards incompatible changes planned for the future except in the alpha and tree directories.  

Music21 v.5 is the first version to require Python 3 (3.4 required.  3.5 or 3.6 recommended as this will be the last version to support 3.4).

Changes since Alpha 2:
  • braille -- accented characters translate to braille
  • features -- many jSymbolic Feature Extractors match the spec more closely (thanks to Micah W. for the patches). Expect more of these improvements throughout the v.5 lifecycle.
  • Bach chorales -- improvements to naming and texts. Expect more of these improvements throughout v.5. Thank you to Dr. Norman Schmidt for these.
  • Improvements and fixes in voiceleading.py -- thanks to Ryaan Ahmed
  • More objects can be hidden with "hideObjectOnPrint"
  • Joplin, Maple Leaf Rag added to corpus
  • Guitar and other fretboards supported. Thanks to Luke Poeppel
  • Improvements to IPython/music21j MIDI
  • Added stream alignment tools in alpha.analysis. Thanks to Emily Zhang
  • docs for Stream.insertAndShift improved greatly.
  • separate zip file for docs.


Download at:
[January 3, 2018 12:35 pm] « » [music21]
The second alpha release of music21 version 5 (Python 3.4+ only) has been released.  There have been 47 new commits since alpha 1 (more on that below) mostly of a maintenance sort.  V5 is still pre-release code, and the syntax is still in flux until the main release next summer, but it is well-tested and good for most hobbyist coding.

Here are the main changes since alpha 1:
  • Better parallel processing system (esp. in terms of docs)
  • Pitches are 30% faster to create, notes are 15% faster.  You do create notes, don't you? :-)
  • Better musicxml support: volume.  Improvements to transposition, glissando, barlines
  • Corpus: added works by Amy Beach, Schubert (Lindenbaum), fixed missing Bach Chorales (thanks Dr. Schmidt!) and error in Haydn op. 1 no. 1 movement 1(thanks Joshua Ballance)
  • Scales, IntervalNetwork: faster and better documented.
  • NeoRiemannian analysis greatly improved (thanks Mark Gotham!)
  • voiceLeading.VoiceLeadingQuartet improved.  compatibility change: improperResolution renamed to isProperResolution and improved.  Former title implied that False meant it was proper; now the title reflects the output.
  • Instrument objects now have their MusicXML v.3 sound tags attached (thanks Luke P.!)
  • Bugs fixed: chords not in voices in measures with voices were not found in some routines. Instrument objects without midiProgram explicitly set get a program on MIDI output.  MIDI no longer inserts a rest at the beginning (thanks KKONZ).  Chord.normalOrder fixed (thanks luiselroquero), bugs in Capella parsing. Bugs related to Apple File System High Sierra not sorting files by default.

I neglected to post on this forum the announcement of music21 v.5 alpha 1, so the many great improvements there are listed below, with a new installation link:

--
Alpha 1 of v.5 of music21 includes an amazingly faster improved version of Chordify (thanks in large part to work by Josiah Wolf Oberholtzer)
music21 v.5 is PYTHON 3 ONLY
Do not upgrade to this version if you are using Python 2.7 (or better still, upgrade yourself to Python 3.6 instead). It runs on Python 3.4-3.6 only.
This is alpha code -- I am still formulating the changes for m21 version 5. Some things that have disappeared since v.4 may reappear, but some things that are currently here may be gone or significantly changed by v5 release. YMMV.
Other big changes:
  • Python 3 only. Yes, I said that but I'm saying it again. This change has made developing much faster and a lot more fun. Also it's made music21 more powerful and faster.
  • Chordify moves from O(n^2) to O(n) time -- Chordify on large scores works great now.
  • MusicXML roundtrip now preserves much about appearance, style, metadata, etc. -- you can now load a musicxml file into music21 and back into your software and 90% of the time you'll get visually the same result as the original software. Finale roundtrip is especially good!
  • Corpora searching is much better and much faster. Metadata is stored in pickle format.
  • Feature Extraction runs multicore by default. Together with the average of 10x faster chordify, feature extraction on large datasets on multicore systems is now very strong.
  • Many routines that used to return string filepaths now return pathlib.Path objects.
  • Almost all deprecated functions are removed.
  • Many keyword functions are now keyword only, so no worries about passing in "inPlace" accidentally.
  • parsing of Volpiano (Gregorian chant notation) added.
  • RehearsalMark is added (and in musicxml also).
  • Empty spaces in MusicXML measures are converted to hidden rests, to avoid gapped streams.
  • Pitches in chords on musicxml import are always sorted from lowest to highest.
  • analysis.transposition -- searches pitch lists for number of distinct transpositions (thanks Mark Gotham)
  • Copyright and other metadata is preserved in many formats on import. This is just being a good neighbor.
  • Demos and most alpha code has been moved to a new separate repository: https://github.com/cuthbertLab/music21-demos -- they will be updated much less frequently. This will also make code development faster. Thanks to all who have contributed to music21's development. We'll be able to get more demos into the codebase by not needing to update them at every moment.
The remarkable work over less than a month has been largely aided by dropping the Python 2 code dependencies, so while upgrading to Python 3.6 might cause some grumbling, my ability to forge ahead quickly I hope will more than make up for it!
This is alpha code. It won't install by default on pip. Use
pip3 install --upgrade music21==5.0.5a2
[August 6, 2017 17:11 pm] « » [music21]
The first release of music21 version 4 was released today (August 6, 2017).  This is the first major release of music21 in a year, and it brings with it a wealth of new tools for analyzing music with a computer and performing digital musicology, music theory, and composition.

Download from https://github.com/cuthbertLab/music21/releases or from the terminal, type:

    pip3 install --upgrade music21

(or without the "3" if you are using Python 2)

Version 4 is the last version of music21 that will support Python 2.7.  If you run Version 4 on Python 2.7, you will see a warning that it's time to move up to the brilliance that is Python 3.6.

As with all new "X" release names, v.4 has backward incompatible behaviors that I think are worth it for the great new features. 
Among the 272 commits since v.3.1:
Major new features:
  • Graphing rewrite!
.plot() and Graphing has always been one of the most powerful parts of music21 since long before v.1.0 (mad props, Christopher Ariza!) but it's also been one of the most daunting aspects of using music21. It shouldn't be any more. The code has gone through a major rewrite to improve the simplicity of doing easy things and the power when doing difficult things. The easy things are documented in Chapter 22 and the hard things in Chapter 44.
  • Local Corpora are great!
There's been a major rewrite of the corpus.corpora.LocalCorpus() function that makes it a fantastic way to work quickly with files you are working on from your own hard drive.  Set up your own local corpus, add paths to it, set the cacheFilePath to somewhere to store the metadata and you'll be able to search for pieces with particular features and metadata without needing to parse the score.

  • Style!
the all new style module and style.Style object handles aspects of a note or other object's visual display that are not (usually) semantic. This class has allowed a major increase in the ability to properly preserve MusicXML visual formatting on input and export.
Style objects are created only when needed, so el.hasStyleInformation() allows for checking for the presence of a .style object without creating one.
(To be documented more soon)
  • Major rewrite of TinyNotation allows for easy extensibility.
Documented in the User's Guide! Check it out!
  • Always improving docs
The User's Guide goes up to chapter 24 now, with major new examples in Chapter 20 along with rewritten chapters on keys, time signatures, sorting, and so on and so on. Plus all examples are now Retina quality for viewing fine details of scores.
Documentation has been moved out of the music21 directory into the root directory -- it is no longer installed with music21 from pip -- this change was necessitated by the move to retina quality graphics, but reduces the installation size from 90MB to 15MB for the full corpus version and 6MB for the no-corpus version.  All documents are now tested with nbval, to ensure they stay up to date.
Other new features
  • Stream.measures() now optionally allows for indexes (where 0 always is the first measure; -1 is the last, and so on) making .getElementsByClass('Measure') not necessary in most cases.
  • much better metadata processing in musicxml, humdrum, and braille
  • improved braille translation (tuplets) -- thanks Bo-Chen
  • better beaming, meter, and tuplets in ABC
  • output directly to PDF if MuseScore is installed.
  • Nested Tuplets! including in MusicXML.
  • Non-traditional key signatures
  • New works by Clara Schumann in the corpus.
  • stream.iterators.OffsetIterator() -- iterate groups of objects by offset.
  • improvements to analysis.discrete
  • demos/build_melody shows how to build MidiFile directly (thanks PeterMitrano!)
  • corpus paths are now searchable in corpus.search()
  • matplotlib and musescore graphics in Jupyter notebook are now retina quality.
  • Chord.add() and Chord.remove() allow for direct manipulation of chords.
  • Improvements to parallel processing in music21.
  • Ottava spanners now come in two types, transposing and non-transposing -- reflecting whether the pitches under the spanner already reflect the transposition (non-transposing) or not.
  • Palestrina humdrum has been reorganized and parses completely.
  • Many improvements to spanners and RomanNumerals.
  • Beams work much better and transfer in and out of MusicXML more completely.
  • Every MusicXML 3.0 articulation is now supported.
  • Core routines in stream.core have now been exposed publicly.  They are dangerous to use, but for anyone working on their own parsers, they can speed up insertions and appends by an order of magnitude.
Others, including bugs squashed:
  • Warning on Python 2 that music21 v. 4 is the last version to support Py 2.
  • Stream.template() is a great way to get an empty stream that otherwise matches the current Stream.  Replaces the obsolete .measureTemplate()
  • ABC key signature and mode error fixed.
  • RecursiveIterator gets a .currentOffsetInHierarchy, which can let even more places remove the dependence on .flat.  In fact, .flat uses the .recurse() method internally, because recurse() is now so fast.
  • AudioSearch bugs fixed (thanks jjrob13)
  • Chord.normalOrderString (thanks emzhang)
  • Removed lots of old crutches including the "analysisData" on Stream, Note.editorial, and others. Style fixes most of this.
  • fix to Bach BWV 386 (thanks alexcoplan) and to Beethoven Opus 59 no 3, movement 1.
  • Note.pitches returns a tuple not list, just like Chord.pitches
  • Converter can deal with some wrong file extensions now.
  • Instrument reprs are fixed
  • configure finds many more notation programs.
  • ties are imported better between elements in and out of voices in musicxml
  • configure works on macOS when user directory contains spaces.
  • Bugs in ending and restarting a recursiveIterator fixed.
  • doc errors fixed (thanks Andrew Sanchez)
  • bestClef() has been moved to the clef module where it belongs.
  • MusicXML sound tag now is placed properly (thanks Almog Cohen)
  • MIDI output from transposed scores now plays in concert pitch.
  • Breves are now acceptable as full measure rests.
Deprecations and deprecated elements removed
  • (this list does not contain changes to the alpha/ directory which can change at any time)
  • Note.ps, and Note.accidental, Note.pitchClass, Note.pitchClassString, Note.diatonicNoteNum, and Note.microtone are all deprecated. Use Note.pitch.ps, etc. instead.
  • Chord.normalForm is deprecated because it gave the wrong answer. use normalOrder instead; same with normalFormString
  • SpannerBundle.list is deprecated; use list(SpannerBundle) instead
  • with the advent of .style, el.color is deprecated, use el.style.color instead
  • Stream.stream() is deprecated -- now that the transition to iterators is done, there should be no need for this.
  • REMOVED stream.getOffsetByElement; use s.elementOffset(el) instead.
  • REMOVED stream.haveBeamsBeenMade; use stream.streamStatus.haveBeamsBeenMade
  • REMOVED stream.makeTupletBrackets(); use stream.makeNotation.makeTupletBrackets(s)
  • REMOVED stream.realizeOrnaments; use stream.makeNotation.realizeOrnaments(s)
  • REMOVED VirtualCorpus -- it may return at some point but with a lot more features.
  • nbconvert is no longer packaged with music21
  • .exe files are no longer generated -- they were rarely used and pip is a better choice for Windows users now.

As the last version of music21 to run on Python 2, version 4 will have a longer support period for security patches and major bug fixes that render large parts of the system unusable for multiple users. This LTS (Long-term support) will run until the clock on python 2 runs out. (Currently two more years and eight months).  After that time, Python 2 will no longer be supported by the Python Foundation, and thus, by music21 either.  We're looking forward to joining the glorious Python 3-only feature and finally get to use some great features to make development faster and more stable.  Music21 v. 5 will be released at about the same time Django v. 2 (Py3 only) and a year after IPython/Jupyter made their first Python 3 only release.  Matplotlib will soon follow.  Python 3 is the future of humanistic and scientific programming.
As always, we thank the community for great support.  We'd always love to hear how you use music21 via the Google Groups mailing list.  Music21 was made possible by grants from the Seaver Institute, the National Endowment for the Humanities, and the School of Humanities, Arts, and Social Sciences / Music and Theater Arts Section at MIT.

How can I contribute?

Music21 is a rapidly-progressing project, but it is always looking for researchers interested in contributing code, questions, freely-distributable pieces, bug fixes, or documentation. Please contact Michael Scott Cuthbert (cuthbert at mit.edu), Principal Investigator.

The development of music21 has been supported by the School of Humanities, Arts, and Social Sciences at M.I.T., the Music and Theater Arts section, and generous grants from the Seaver Institute and the NEH/Digging-Into-Data Challenge. Further donations to the project are always welcome.