GSoC 2012

What is Google Summer of Code?

It is a global program run by Google that offers students stipends for working on open source software projects during summer vacations.

The LilyPond Team decided that this is an excellent opportunity to find new contributors and encourage students already participating in LilyPond development to become more involved. One of our contributors was accepted for 2012 edition of the program as part of the GNU project; we hope to participate in future editions as well.

Our 2012 Ideas List

Below is a list of projects that we suggested for GSoC 2012 students. Although the application period is over, we decided to keep this webpage online as an inspiration for anyone who is interested in developing LilyPond. Some members of the development team are willing to help people who would like to tackle these projects.

Of course, there are many more things to improve in LilyPond, including very small ones. A full list of all known issues can be found here.

Grace notes

Fix problems with synchronization of grace notes, together with all underlying architecture (see issue 34 in our tracker). Grace notes are confusing to LilyPond’s timing because they’re like going back in time. This causes weird effects, especially when one staff has a grace note and the other doesn’t.


Requirements: C++, MIDI

Recommended: familiarity with LilyPond internals

Mentor(s): Mike Solomon, Carl Sorensen


Adding comprehensive MusicXML export and improving import, together with tests checking that it works. Depending on time available, implement some or all of the following:

  • Handle basic musical content export like the MIDI export (i.e. using dedicated exporter classes, derived from the translator class)
  • Build the XML tree of the basic musical content, add a connection from music event to XML tag
  • Let all LilyPond engravers do their job
  • Add ability to link each output object (basically each stencil / group of stencils) to the music cause (and thus to the XML tag in the XML tree)
  • Add a XML output backend, which can then add the layout information for each output object to the XML tags

The goal will be considered achieved when a (previously chosen) score could be imported from MusicXML and exported back with no unintentional loss of data.


Requirements: MusicXML, Python, basic LilyPond knowledge

Mentor(s): Reinhold Kainhofer, Mike Solomon

Familiarity with other scorewriters (for cross-testing) would be a nice bonus.

Improve slurs and ties

The default shape of slur and tie curves is often unsatisfactory. Ties on enharmonic notes { cis'~ des' } are not supported, ties "broken" by clef or staff change aren’t supported well. The project includes collecting and sorting examples of bad output, deciding on the intended output and writing the actual code.


Requirements: C++, experience with writing heuristics

Recommended knowledge: LilyPond knowledge, aesthetic sense

Mentor(s): Mike Solomon

Adding special variant of font glyphs

Adding on-staff-line, between-staff-line, shorter and narrower variants of some glyphs, for example accidentals, together with a generic infrastructure to support them. An example is ancient notation breve notehead coming in two variants, with smaller and bigger hole.


Requirements: MetaFont, C++, good eye for details

Recommended knowledge: basic LilyPond knowledge

Mentor(s): Werner Lemberg

Improve beaming

Default positioning of regular, cross-staff, broken and kneed beams should be improved. Beaming should depend on context and neighbor notes (see section 2.2 here). If possible, reduce beaming computation time.


Requirements: C++, experience with writing heuristics

Recommended knowledge: aesthetic sense

Mentor(s): Mike Solomon, Carl Sorensen

Clean up various compilation warnings

Clean up compiler warnings, static code analysis, and valgrind warnings. Automatic code analysis tools (warnings in g++ and clang) and analysis tools like valgrind memory leak detection and callgrind code profilers provide valuable information about possible flaws in C++ code. Cleaning these warnings would allow us to automatically reject any patch which introduced extra warnings.


Requirements: C++

Mentor(s): Joe Neeman, Reinhold Kainhofer


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