Monday, August 22, 2016

music21 v 3 Released (3.1.0)

Version 3 of music21 is here!  This is the first major release in 11 months, with nearly 600 commits since the last version.  As a new major version, there are both huge new features as well as significant (often backwards incompatible) changes.

Upgrades for most users should work automatically by typing:

   pip3 install --upgrade music21

or (Python 2)

   pip install --upgrade music21

Or download from GitHub

A summary of the most important changes since v.2.2 are below:

Fun and easy to understand changes:

Lots more MusicXML support -- better support for time signatures, for grace notes, for spanners, for metadata, name it!  And the system is refactored in such a way as to make contributing missing features quite easy.

MIDI files play back in Jupyter/IPython contexts.  Lots of improvements there for people who use MuseScore.

The User's Guide has become much more awesome, and you can play with all the good features there.

Many new ways to search scores -- LyricSearcher is fully polished and documented in the User's Guide.  Carl Lian's search.serial is upgraded from alpha to a full release that will be easy to expand in the future -- want to know where certain motives are used or transformed? This will make it easy to do. And search.segment -- the old standby -- is even better than ever (see below)

Try splitting notes and recombining them -- lots of intelligence going into this.

There's a big difference between taking a passage up a major third and taking it up 4 semitones.  In Chromatic contexts, music21 will now spell things how a musician would like to see them.  If you're working with MIDI data, without explicit enharmonics specified, you'll appreciate this.

Go ahead and use '~/../dir' and things like that in your file parsing -- music21 groks all that.

Look at you, fancy programmer, with your 4-CPU laptop! Why not give common.runParallel(tasks, function) a try and get music21 working 2-3x faster than before?  (just make sure that "tasks" isn't a list of Streams).  Oh, and if you're using search.segment to search for a particular passage inside a large collection of files, don't worry about using runParallel -- we'll do that for you automatically.

Docs are pretty and much better.  The User's Guide is the place to start.

Too many other changes to mention, but some shoutouts to Shimpe for new Lilypond code (triplet chords, etc.), Frank Zalkow for enharmonic spelling , dynamics, tempos and other things,  Chris Antilla for continued dedication to MEI processing, Emily Zhang for hashing functions and speeding up MIDI quantization,  Sonovice for articulation handling,  Dr. Schmidt for Chord symbol translations, Bagratte for IO cross Py2/3 fixes, Bo-Cheng Jhan for great braille contributions.

Big under the hood changes.

Big, backwards incompatible change: Many calls such as .parts, .notes, .getElementsByClass(), .getElementsByOffset(), etc. no longer return Streams.  They now are iterators (returning something called a StreamIterator).  For most uses, this is not going to change anything.  You can still use: for n in myStream.notes: and it'll work great. It makes many parts of music21 much, much faster.  For small scores, the differences will be small.  For large scores, the differences will be tremendous, especially when filters are chained, such as: myScore.recurse().notes.getElementsByClass('Chord').getElementsByOffset(0.0).  You're going to find that writing iterator chains is an amazing way to only get at items you want, especially with custom filters.  To get the old behavior, just add .stream() to the end of your iteration.

Because none of these filters change the activeSite of an element, you'll find that this is much more stable than before.

If you want to know what the note after a given note is in a musical context, call or n.previous().  If it's the last note of a measure, it'll move on the first note of the next. And once you've called .next() on one note of a stream, the remaining calls will be super super fast. I still haven't wrapped my mind completely around this paradigm, but it sure beats all the fooling around I used to do to figure out if one note was the same pitch as the next one, etc.

If you've been using music21 for some time, but have never looked at the docs for base.contextSites(), do it -- this is a very fast and extremely powerful way of figuring out how two objects relate to each other.  Together with the .next(), .previous(), and better support for .derivation, many extremely powerful systems can be written in music21 easily that could only be written with huge difficulty before.

Nearly all functions marked deprecated in v.2. have been removed.  Lots of super obscure functions in .base.Music21Object or .sites.Sites are gone.  This is a positive step since it'll make the documentation for these objects simple enough to understand.

Sorting works.  I mean, it just works.  With grace notes, with oddly positioned elements, with what have you. And it's pretty darn fast. This might seem like something small, but it's enormous for us.

Corpus managing is much simplified -- if you ever thought in the past, "Hey, I'd like to use a custom corpus" and then thought, " thanks..." give a look at what is needed to set one up now.  You'll be glad for it!

Musescore and not Lilypond is used in Jupyter/IPython notebooks.

Complex durations are a lot less complex -- and faster.  

PyLint on all code -- I estimate that at least 200 undetected bugs vanished through this major effort. 

The Future

As noted in messages to the music21 mailing list (music21list at Google Groups), v.3.1 is the first non-beta release in the v.3 lineup.  Version 3 happens to share a version number with Python 3, but that is merely coincidence.  Music21 version 3 continues to work with Python 2.7 as well as Python 3.4.  Version 3 adds explicit support for Python 3.5 and drops support for Python 3.3. Music21 will continue to develop into a Version 4 to be released next summer (4.0.x will be alpha and beta releases and 4.1.0 will be the public release).  Version 4 will likely be the last version to support Python 2.

This release represents the end of a year's sabbatical where I got to work on low-low-level music21 functions that I didn't think anyone else would want to.  Due to teaching and other obligations, I'll be taking off work on the heart of music21 until the holidays (I'll still be taking bug fixes, etc.) and working more on documentation, examples, and applications.  The changes put in place for music21 v.3 has made working with it a lot more fun for me, so you'll probably see more a lot more applications get added, first to the alpha directory and then into the main set.  I've also put up a version 4 roadmap (trees are almost done, they should make it in. Style objects will be introduced so that beautiful musical scores can be created or at least imported and exported properly without major speed loses) so if anyone wants to take the lead on a project you can do so.  I'm working on a project called STAMR, Small Tools for Agile Music Research, which should create standalone tools using music21 and music21j for musicologists to get their work done faster.  Given that I'm teaching music fundamentals online again, you should see music21 and music21j integration working far better than ever before.

Thanks to MIT for supporting my work, and the Seaver Institute and the NEH for initial funding to make music21 a success.  And thanks to this great community for all your contributions in the past and contributions to come.

Wednesday, August 3, 2016

music21 v. 3 beta-3.0.6 released

A release candidate of version 3 of music21 (3.0.6) is available now as a package on GitHub.  As a beta release it's still not 100% ready for general usage, so "pip install music21" will still install version 2.

Get it at: 

This is likely to be the Release Candidate also for music21 v.3.  I've indicated several times in the past that music21 v.3 is the last release that I guarantee will continue to support Python 2.  I now suspect that there will be a Python 2.7-compatible v.4, since Python 2.7 is still the shipping version of Python w/ macOS Sierra.

Notes about the substantial changes in Version 3 have been posted on this list several times.  The biggest changes are that .getElementsByClass() and .notes, etc. all return a new class called a “StreamIterator” which makes working with stream filtering much much faster than before, especially for very large streams. 

The new tree-based storage system is still too flaky to turn on by default except in a few cases, and will be deferred to Music21 v.4.

Laundry list of items changed since 3.03-alpha:

min Python 3 version is now 3.4 -- 3.3 should still work but is untested.Notes parsed from MIDI or transposed by a number of semitones now get a .spellingIsInferred attribute which indicates that they can change their spelling ("G#" vs "A-") as needed for the situation. This is incompatible behavior, but much improved!
More User's Guide chapters...
Lots of improvements to Braille output, and refactoring to make more improvements in the future possible. (Thanks Bo-Cheng Jhan! and esp. to Jose Cabal-Ugaz in the first place).
Better documentation for Searching Lyrics (User's Guide, Chapter 28)
MIDI will now handle part names, etc. that use unicode.
Long files (>10 pages) in Musescore automatic PDF generation format now work (thanks Emily Zhang)
TimeSignatures such as 2/4+3/8 display much better now.
TimeSignatures import and export symbols ('common', 'cut', etc.) in MusicXML properly.
Fixes for musicxml parsing where both voices and chords interact. now finds common MusicXML readers (Finale, Sibelius, MuseScore) on Windows!
InsertIntoNoteOrChord works in more cases
Streams are faster to calculate their own durations
Major speedups to large makeMeasure() calls.
A failure in makeTies now gives a warning instead of an exception
The old "musicxmlOld" format is removed. 
metronomeMarkBoundaries works better (thanks Frank Zalkow!)
improved ability to specify how to quantize MIDI (thanks EZ!)
improvements to automatic instrument detection.
lots more MEI articulations work (thanks sonovice)
Fingerings import and export to MusicXML better.
noteheadParentheses work well now.
Roman.fromChordAndKey gets quite a few more chords now.
incompatible change: normalOrder instead of normalForm for chords -- gives the untransposed ordering of a chord -- this is the correct behavior; prior behavior is wrong.
incompatible change: Stream.offsetMap is now a method
incompatible change: common.isStr() removed -- use isinstance(s, str) or (s, (str, unicode))
incompatible change: key.KeySignature() no longer supports a .mode attribute.  Use key.Key() instead.  key.KeySignature() objects get an .asKey('major') etc. attribute.
incompatible change: pitches lose ".getMidiPreCentShift()" method.  Just call .midi instead!

in case you missed what is new in v.3.0.3:

Python 3.5 compatible.
Splitting notes via .splitXXXX() is now much safer and more efficiently
Many, many parts of music21 can now use multiprocessing efficiently (see common.misc.runParallel())
BUG: Haydn Opus 74no2 was not actually ever in the corpus and has been removed.
Several MEI bugs fixed (thanks Chris Antilla)
Better automatic generation of chords from pitch classes (thanks Frank Z.)
Triplet chords work in lilypond
midi.realtime works with PyGame on Python3. and .previous() work well and FAST 99.99% of the time.  (see docs for the tiny case when it might be a problem)
Many routines that used to return tuples now return NamedTuples
Many deprecated routines removed — code is simpler to use
Working with multiple corpora now has “only one way to do it” — simplify.
.show(‘midi’) works in IPython.

Much more documentation

Monday, July 18, 2016

ContourViz: Creating Interactive Contour Visualizations from the Command Line

Despite the author name, this is a guest post from Christopher Witulski; he can be reached at  chris.witulski at  We thank him for sharing this exciting pre-publication work. -- MSC

Last year I learned about music21 and ever since I have been wondering how I can use it to learn more about the Moroccan musical repertoires that I study. Long story short, I ended up building a tool for creating interactive web-based contour visualizations from the command line and I'd like to share it here.

Climbing out of a rabbit hole

I was working through a project and struggling to keep track of things. The paper was an analysis of a genre of Moroccan sung poetry called malhun for the 2016 Analytical Approaches to World Music conference. The performance of each poem can last twenty-ish minutes and contains a number of repetitions of the refrain text. These refrains are short (roughly eight 2/4 measures long) and modulate through repetitive--but different--melodies. I had transcribed over sixty of them in an attempt to understand how they worked, how they changed, and how they were related to each other.

Musicians on stage, with a solo singer in front and the author among five violinists holding his in Western style
Malhun Performance in Fez, Morocco

Having performed this music in Morocco (I'm the lone violinist in the photo who can't quite figure out how to play while holding the instrument upright on my knee), I was constantly struck with this feeling of déjà vu. New melodies felt so similar to old ones, but I could not put my finger on how or why. The problem was simple: I could not keep sixty or seventy different transcriptions in my head at once. Comparing them was getting tricky. I wanted a way to stack them on top of each other, almost as if I could print the transcriptions on a transparency and show them all at once on an overhead projector.

Over the previous months, I had been teaching myself Python in an effort to learn more about music21 and what it could do. It was time to try and build the tool that I needed instead of wishing I could find it.

Visualizing contours

For the presentation, I put together a small library that carried out two main tasks. First, it used music21 to parse my transcriptions, normalize the length of each melody, and build a dataset. Using offsets, frequencies, and distances from the final note of each melody, it turned note objects into a JSON of coordinates. At 1,000 different y values (each corresponding with 1/1,000th of the length of the total melody), it measured an x value for the frequency and one for the "distance from the root," the distance in steps above or below the melody's final pitch.

Visualization of 68 Melodic Contours from Malhun overlaid with one labeled in bold red
Malhun Contour Example

The JSON was passed to another library that I had been recently learning and working with called D3.js. It is written in JavaScript and designed for creating powerful interactive data visualizations. I supplemented my presentation with an online chart of each of my malhun transcriptions: by grouping contour lines within each poem, I was able to easily see the source of my déjà vu. Despite changes in pitch content, range, root motion, and a host of other things, the contours themselves often stayed strikingly consistent throughout the long performances. You can see the visualization and click through the different poems online, though be aware that some parts (like the "Next" button) are artifacts of the paper presentation.

Building a tool

Maybe two weeks ago I decided to try my hand at creating a Python library of my own. I simplified the chart, creating a sort of template, remove the stepwise element of the visualization, and fought my way through learning to upload a project to PyPI. The result is ContourViz... I didn't give much thought to the name, my apologies.

"Three Melodic Contours" -- one is shown in blue.
ContourViz, simple example

The tool takes, as an argument, either a music notation file or a directory with many of them. It parses these files and creates a JSON structure of 1,000 coordinates for D3.js to work with. It then copies a folder called results that includes an index.html file and a folder of JavaScript and CSS files that the generated web page will use into the current directory. Finally, it runs the Python SimpleHTTPServer and opens the new page, parsing the JSON to create the visualization.

You can install ContourViz using the following in your terminal:

pip install contourviz

It runs from the command line, so creating a visualization of multiple melodies, like the one above, is as easy as:

chart-single-contour '/path/to/file.xml'

Working with a directory is similar:

chart-contours '/path/to/directory/full/of/xml/or/mxl/files'

6 Melodic Contours -- more complex chart showing 2 x three overlapping contours from Damlij-Bouzouba
ContourViz, more complex example
I'm still toying with the system and it has a number of issues. For example, I would love for it to parse voices as individual melodies if they are present. Instead, it only works with monophonic lines, meaning that each voice has to be in an individual file if you wanted to visualize voice leaning or other contrapuntal patterns. There are smaller issues: I still need to set up the Y axis to render note names properly.

Please feel free to check out the GitHub repo and suggest any other changes or ways in which it could be more helpful. This is my first go around at building a tool of this sort, so I am eager to hear if it is helpful and how it could be improved. And thank you for allowing me to join the community.

Tuesday, July 12, 2016

Using music21 for Jazz Improv and Study

The following is a guest post from Daniel McGillicuddy, alias Basso Ridiculoso.  He can be reached at daniel.mcg [at]   -- MSC

Hello all!

I am a gigging musician and bass player who has discovered music21, but, alas, I am certainly not a musicologist or academic.

I have seen many of the amazing examples that showcase music21’s capabilities with classical and twentieth-century music, and wanted to show how I use music21. Hopefully these examples show that music21 can also be used to explore jazz and popular music, either via analysis for educational purposes or for developing improvisational ideas.

Jazz Standard Voice Leading Lines

Music21 has an amazing corpus of public domain classical music, but most jazz standards are not available for inclusion. But, since music21 has an understanding of seventh chords and reads MusicXML, a virtual corpus of jazz standards is available for analysis and exploration via another application called IRealPro. IRealPro is a virtual accompanist software program that has chord charts for over 3000 jazz standards, and which can export the chord progressions in MusicXML, a format that will allow music21 to understand the harmony. Once we have that outline of a jazz standard's harmonic structure, music21 can be turned loose.

For this example, lets export the chord chart to the standard “Alone Together” and generate a 3rd to 7th voice-leading line through the entire tune, based on this concept by Burt Ligon, as described here.

(links: Alone Together.XML and Guide Tone Lines with

Since music21 understands harmony, any kind of voice leading line is possible, for instance the 5th resolving to the 9th. Now these voice leading lines can be generated for any jazz standard (or for any chord progression) that can be exported as MusicXML format and these lines can be used as jumping off points for making solos or studying voice leading.

Jazz Solo Analysis 

Analyzing jazz solos from the masters is another way to get improvisational material, but it is better known as stealing someones licks! Since music21 can understand the relationship of any note to any chord, it can be used to analyze the functional relationship of the notes in a solo.

Here is an example of Miles Davis’s solo on “Freddie Freeloader” with the notes being labeled so they represent their function against the chord being played, for example, an F note on a Bb7 chord being the fifth.

(links: Miles Solo XML  and Melodic

This same Music21 code was used to analyze Charlie Parker's solo on Bloomdido, and a walking bass line over F blues by Ron Carter.

Now any solo line that can be exported as MusicXML can be analyzed by music21 and then explored even further. What notes are favored? What beats of the bar do certain notes get played on? How many times do certain notes get played? Are there repeating phrases that a certain player uses over and over? All of this can be cataloged or graphed once it has been brought into the music21 world. The included code needs a chord symbol over every measure.

Hopefully these examples show that music21 is not only for musicologists exploring the pitch class space of Bartok's string quartets or for twelve-tone row composers! Students and musicians can use it for very useful and practical purposes as well. Many thanks to Michael for allowing this guest posting from big music21 fan!

(Ed: Thanks Dan! The examples included here are copyrighted by their respective composers and publishers. We believe their inclusion here for educational and instructional purposes are supported by all four factors of the Fair Use test).

Friday, October 2, 2015

"Data in a Major Key": MIT Spectrum, FSU

MIT Spectrum has an article by Kathryn M. O'Neill on my work, music21, and computational musicology:
“IF I WANT TO KNOW how the guitar and saxophone became the important instruments throughout classical repertory or how chord progressions have changed, those are questions musicology has been unable to approach,” says Associate Professor of Music Michael Cuthbert. Spotting trends and patterns in a large corpus of music is nearly impossible using traditional methods of study, because it requires the slow process of examining pieces one by one. What his field needed, Cuthbert determined, was a way to “listen faster.”

In other news, Clifton Callender at Florida State University is currently teaching a doctoral seminar on music theory techniques using music21.  His course description is at

Monday, September 28, 2015

Music21 v. 2. (non-beta) released!

The long-awaited (at least by me) version 2 of music21 is released!  This is the first version of the v.2 release to be out of beta and stable enough for general use by everyone.

Upgrade with:

    pip install --upgrade music21

Or download from GitHub.

The first non-beta release of music21 since v. 1.9.3 (June 2014) gives a ton of new features and lots of new speed.  But being a major release change number, it also has some changes that every programmer using the system needs to be aware of.  The release notes on GitHub gives all the details, but here are the highlights since 1.9:

Changed and Added features

* Duration and Offset now use Fractions when necessary for exact representation of tuplets. Many, many errors from rounding are gone.  For now, you can use Duration.quarterLengthFloat and offsetFloat to get the old behavior, but float(Duration.quarterLength) and float(offset) are better.
* Converters support easy to install custom sub converters. MEI is now supported (thanks to McGill university)
* Python 2.6 is not supported.  Python 3.4 is highly recommended; 2.7, 3.3, and 3.5 also work.
* Loading cached streams is extremely fast. All streams are automatically cached when loaded from disk.
* Sorting is much more consistent and faster
* MusicXML parsing and showing have been rewritten to use cElementTree and many new features.
* Stream's internal mechanisms have been hugely rearranged.  Now offsets are stored inside Streams instead of inside Notes, etc., making lots of things faster and more reliable.
* Streams support filters on iteration using the `.iter` property and the `recurse()` method.  These are big changes for speed and reliability.
* Namedtuples replace anonymous tuples in many places
* Music21 is available under the BSD license.
* Musedata files are no longer available in the corpus. However, new files in MusicXML format have replaced several of them.
* Complete rewrite of TinyNotation making it much easier to subclass for your needs.
* If you have MuseScore 2, try'musicxml.png') to get a beautifully rendered musicxml file. Or use .pdf to get something ready to print.  Thanks Nicholas, Thomas, and Walter!
* Builds are automatically tested for errors and documentation coverage.
* Experimental modules moved to the `alpha` sub package.  `demos` reorganized.
* Lots of documentation changes!
* Obscure and almost never used (or actually never used) methods and attributes have been removed.
* Did I mention how much better the documentation is getting?

In case anyone is keeping track, since v.1.0 (June 2012), here are the:

Biggest changes between 1.0 and 1.9

* Store complete Streams via FreezeThaw
* Output to Vexflow and `music21j`
* Converters have been moved into packages.
* It takes 1/3 the time to do most operations, and 1/4 the time to start up.
* Capella supported.  ABC imports almost everything. Humdrum supports multiple voices. Chords have a better root() algorithm
* Many, many new corpus pieces.
* Layout support.
* Python 3 supported, and now recommended.
* Timespans make .getContextByClass at least an order of magnitude faster, letting music21 handle huge scores.
* Derivations reduce the number of Streams to keep track of.

Oh, and I did more than patch bugs in the last week:

Release notes since 2.0.11

* Streams use .iter and .recurse() in TONS of functions, making many a lot faster, a few a bit slower, but all cleaner to debug and safer.
* Deprecated items now return a deprecation warning.
* Duration objects now have a `.client` which can inform the `Note` of changes to it.
* `.classes` searches are way faster. Returns tuple.
* `deepcopy` is about 30% faster.
* `common` is split into a directory of related functions.  Now worth looking through.
* all corpus files, including small .abc files with non-standard additions, now parse.  A complete should be possible without any try: statements.
* several bugs in musicxml processing (mainly related to the handling of expressions, noteheads, etc., on chords) have been fixed.  Also Finale's `` tag is supported.
* code is much more "lint-free" catching many subtle bugs.
* audioSearch is cleaned up, with beta-type code moved to demos.
* Documentation much improved including three new User's Guide sections, and (thanks to bagratte) fixes for UTF-8 errors.
* `` replaces `` for better non-Western script handling.
* .egg files are no longer distributed.  I'll work on getting .whl (wheel) files soon, but for now use .tar.gz.  PyPi no longer supports .egg, so there's no reason for them.

 incompatible changes

* `.fullyQualifiedClasses` is GONE. No one used it.  Instead a new `.classSet` replaces it for rapid class searching.
* sites.Sites and sites.SiteRef are no longer imported into base by default.
* `documentation` modules reorganized, with better examples.
* `stream.core` moves several core modules out of the `stream` module.
* `Volume.parent` renamed `Volume.client` to match `Derivation` and `Duration`
* `.components` on `Duration` now returns a tuple.

What's Next?

Today also announces the first commit of music21 3.0 -- for the first time, I'm going to try to do something daring: keep bug fixes and some backwards compatible changes in the 2.1 (2.2, etc.) branch, but go forward with bigger changes in a 3.0-alpha branch.  Some things that you might expect to happen:

* All deprecated functions will be gone in 3.0; like immediately; like I'm deleting them as I type.

* Lots of things that currently return a Stream will instead be iterators over Streams.  These include: .getElementsByClass(),  getElementsByOffset() -- the fact that so many streams get created is one of the biggest headaches and reasons why the system gets slow.  You can prepare for the change by examining your usage of these functions and asking yourself, "Am I actually using this as a Stream? Or just as a bunch of objects to iterate over in a for loop or to count using len()"?  If the latter, you're fine.  If the former, go ahead and add .stream() after it, for instance filteredStream = s.getElementsByClass("TimeSignature").stream().  The last `.stream()` call does NOTHING right now, but it will ensure that your code works exactly the same after the change happens.  If you want to use the new features (even in 2.1) add .iter between `s` and `.getElementsByClass()` (but leave off the `.stream()`.  You'll find that life will be going a lot lot lot faster.

* I'm going to make a second attempt to use TimeSpans as a general storage engine for Streams.  These are the super fast representations of Streams that Josiah Oberholtzer made, that speed up working with large streams by 10-100x. But for very small streams (such as one measure of a Chorale), they are much slower than the current Streams. Now that all the core mechanisms are factored out of Stream into StreamCore, I can play much more easily with switching in any out the backend functions. Using the lessons of Python's TimSort, I'll probably have the TimeSpan core kick in immediately when there are more than 64 elements in a Stream; it should be seamless except for a tiny delay when the 65th element is added (like shifting gears in a car).

* I may make Python 3.4 a requirement.  We'll see... I'm sick of coding for Python 2.  Python 3 is much more fun from the coder's perspective.

Thanks everyone for great support! -- Myke

Monday, September 21, 2015

Music21 v. 2.0.11 released

Ten days since the last release, so time for a new one. Again, speed, stability, and new features. The biggest change is the entirely new MusicXML output system to match the entirely new input system introduced last release. 
The second biggest is in the (re)introduction of StreamIterators and RecursiveIterator. I'll need to get some demos up of this soon, but this will be a game changer for some tasks.
Update or install with one (or both) of these commands: 
pip install --upgrade music21
pip3 install --upgrade music21

Bigger changes
  1. MusicXML now uses the faster, more reliable ElementTree output generator. Please report any bugs on import or export, especially if they are regressions from format='oldmusicxml'oldmusicxmlwill disappear soon.
  2. Better docs (see below), especially for the long under documented recurse function. Everything that was in overview is now in the User's Guide.
  3. Streams now support filters on iteration -- if you have been using: for e in s.getElementsByClass('X'), try: for e in s.iter.getElementsByClass('X') for a major speedup, especially if you just want the first one or something of that sort. Recurse() supports the same, so for e in s.recurse().notes.getElementsByGroup('tuba') will be WAY faster than before. You might not notice the difference on your own work, but internally things are getting a lot faster. (obscure non-filter routines will be deprecated and disappear soon).
  4. Corpus docs/indexes, etc. are updated with more recent corpus changes (nothing new, but easier to find).
  5. Use of deprecated functions now generates a warning. This should help people plan for migration in case you're not reading the documentation religiously.
Smaller changes
  1. Documentation is improved and updated working with Jupyter/IPython 4 (note: a bug in nbconvert + pandoc requires pandoc v. 1.33 or older to make; they're working on a patch). Docs build in parallel, so it's very fast -- you'll see updates more often.
  2. Documentation is now separated into "source/" and "autogenerated/" folders -- everything in source is user editable. Nothing in autogenerated is.
  3. A number of obscure, long deprecated functions are gone, the biggest being n.removeLocationBySite() use n.sites.remove()
  4. normalization in features has been fixed (Thanks Frank Zalkow)
  5. Parsing of cappella MusicXML files has been improved.
  6. Improved parsing of RomanText files; bugs in several encodings of rntxt and abc files have been fixed.
  7. common.nearestCommonFraction has been renamed addFloatPrecision to better reflect what it does. This has always confused me.