B.M. Azevedo and J.J. Almeida 205 abc is a musical notation standard and not a software package. abc was later expanded to provide multiple voices (polyphony), page layout details, and midi commands. An abc tune has a header with fields for title (T), composer (C), key signature (K), time signature or meter (M) and default note duration or length (L). The music is notated using the letters A (lá) to G (sol) to represent the notes. The notation has a simple and clean syntax, and is powerful enough to produce professional and complete music scores. Among other advantages, the following are the most important: powerful enough to describe most music scores available in paper; actively maintained and developed; the source files are plain text files; this format can be easily converted to other known formats; there are already tools for transforming and publishing abc, such as, abcm2ps [18] and abc2midi [1]; compact and clear notation; human readable; thousands of tunes available on the Internet; abc was adopted in this work in order to cope with real world problems that occurred in the project WikiScore [2]. 2.2 Projects and Tools In this subsection we discuss some the most relevant projects and tools being developed or used at the moment1 . abcm2ps [18] A command line program which translates music written in abc music notation into customary sheet music scores in PostScript or SVG format. It is based on abc2ps 1.2.5 and was developed mainly to print Baroque organ scores that have independent voices played on multiple keyboards and a pedal-board. The program has since then been extended to support various other notation conventions in use for sheet music. Moreover, it is now one of the most complete abc implementations. It is developed in C language and the author, an organist and programmer called Jean- François Moine, releases “stable” and “development” versions of his program. As of this writing2 , the stable release is 6.6.22 and the development release is 7.5.2. Since release 7.2.1, abcm2ps tries to follow the abc standard version 2.1. abc2midi [1] A program that converts an abc music notation file into a midi file. It is part of the abcMIDI package, which includes other utility applications. The program was developed in C language by James Allwright in the early 1990s and has been supported by Seymour Shlien since 2003. The program contains many features, such as expansion of guitar chords, drum accompaniment, and support for micro tones which do not exist in other packages. Music21 [8] A Python-based toolkit for computer-aided musicology. Music21 is a set of tools for helping scholars and other active listeners answer questions about music quickly and simply. Music21 builds on preexisting frameworks and technologies such as Humdrum, MusicXML, MuseData, midi , and Lilypond, but Music21 uses an object-oriented skeleton that makes 1 A more extensive list of abc software may be consulted in http://abcnotation.com/software#linux 2 20th May, 2013. SLATE 2013