STANDARD MUSIC FONT LAYOUT (SMuFL)

Digital typefaces containing the symbols used in Western common music notation have been in use for 30 years, but the development of the repertoire of symbols that are included, their assignment to code points, and design considerations such as glyph metrics and registration, have been rather ad hoc. The Standard Music Font Layout (SMuFL) establishes guidelines for all of these areas, and a reference implementation is available in the Bravura font family. Software developers and font designers alike are beginning to develop implementations of SMuFL in their products, and benefits including easier data interchange, interoperability of fonts with a variety of software packages, are already being felt. 1. A BRIEF HISTORY OF MUSIC FONTS Computer software has been displaying musical symbols of various kinds since the 1960s, but the first font for musical symbols did not arrive until 1985, when Cleo Huggins designed Sonata for Adobe. 1 Sonata mapped the musical symbols onto keys on the standard QWERTY keyboard, using some simple mnemonics (the treble G clef, for example, was mapped onto the & key, and the sharp sign onto #). Most music fonts developed since then, including Steve Peha’s Petrucci (the first music font for the commercial scoring application Finale, dating from 1988 2 ) and Jonathan Finn’s Opus (the first music font for the commercial scoring application Sibelius, dating from 1993), have 1 See http://www.identifont. com/show? 12A 2 See http://blog.finalemusic. com/post/2010/02/18/Meet -Steve-Peha-creator-of-Petrucci-Finales-firstmusic-font.aspx followed Sonata’s layout. However, since Sonata includes fewer than 200 characters, and even conventional music notation 3 requires many more symbols than that, individual vendors have devised their own mappings for characters beyond Sonata’s initial set. By 2013, for example, the Opus font family that is still Sibelius’s default font set contains no fewer than 18 fonts with more than 600 characters between them. In 1998, Perry Roland of the University of Virginia drafted a proposal for a new range of musical symbols to be incorporated into the Unicode Standard. 4 This range of 220 characters was duly accepted into the Unicode Standard, and is found at code points U+1D100– U+1D1FF. 5 However, its repertoire of 220 characters does not extend dramatically beyond the scope of the original 1985 version of Sonata, though it does add some characters for mensural and Gregorian notation. To date the only commercially available music font that uses the Unicode mapping is Adobe Sonata Std, and its repertoire is incomplete. The designers of other music applications have developed their own approaches to laying out music fonts that are incompatible with both the Sonata-compatible approach, and the Unicode Musical Symbols range. In short, existing standards are either ad hoc or insufficient for the development of fonts for rich music notation applications. 2. GOALS FOR A NEW STANDARD Steinberg began work on a new scoring application at the start of 2013, and quickly identified both the need for a new music font, and the lack of an adequate standard for the layout and design of such a font. Surveying a range of commercial, open source and freeware music fonts from a variety of sources, and 3 A term coined by Donald Byrd, Senior Scientist and Adjunct Associate Professor of Informatics at Indiana University. 4 The original proposal is no longer available, but an archived version can be found at http://archive.is/PzkaT 5 See http://www.unicode. org/charts/PDF/U1D100.pdf Copyright: © 2015 Daniel Spreadbury et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. considering the needs of the in-development application, provided the impetus to create a new standard, with the following goals identified from the outset: 2.1 Extensible by design The existing Unicode Musical Symbols range is a fixed set of 220 characters in a fixed range of 256 code points at U+1D100–U+1D1FF. This range is not easily extensible, though of course it would be possible for one or more non-contiguous supplemental ranges to be added to future versions of Unicode. Sonata pre-dates the introduction of Unicode: in common with other PostScript Type 1 fonts of its age, it uses an 8-bit encoding that limits its repertoire of glyphs to a maximum of 256 within a single font. Fonts that broadly follow a Sonata-compatible layout are therefore likewise limited to a maximum of 256 glyphs, and as their developers have needed to further expand their repertoire of characters, they have unilaterally added separate fonts, with no agreement about which characters should be included at which code points. A new standard should be extensible by design, such that even if the repertoire of characters needs to expand, there is both a procedure for ratifying the inclusion of new characters into the standard, and a means for individual font designers or software developers to add glyphs for their own private use in a way that does not break the standard for other users. 2.2 Take advantage of modern font technologies The development of the Unicode standard and the OpenType font specification, and their adoption by operating system, software, and font developers, are both enormously important: Unicode provides categorization and structure to the world’s language systems, while OpenType enables the development of more advanced fonts with effectively unlimited glyph repertoires and sophisticated glyph substitution and positioning features. A new standard should enable software developers and font designers to build software that takes advantage of these features, without tying the standard to a specific set of technologies, so that it is as broadly applicable and resistant to future obsolescence as is practical to achieve.