A WEB-based Approach to Music Notation using GUIDO

This paper describes how exible, online conventional music notation (CMN) can be obtained using the powerful music description language GUIDO in conjunction with the WEB-based GUIDO NoteServer. This fast, exible, easy to use, and portable approach to platform-independent music notation can be used for a broad range of applications, for example to display conventional music notation on WEB-pages or to realise score displays in musical applications. Introduction and Background Today's conventional music notation can be traced back to Guido d'Arezzo (ca. 992-1050), the inventor of the sta system for notating music. Even though some graphical and musical symbols have been added or changed as musical composition and performance techniques evolved, the basic concept of representing duration and pitch in a two-dimensional graphical way has remained the same. It is well known that conventional music notation is not well suited for representing music within computers and much work has been done to nd other suitable digital representations of musical material (see, e.g., [Selfridge; 1997], [Grande; 1997], [Hewlett, Selfridge; 1997], [Sloan; 1997], [Rotterdam; 1998]). So far, for various reasons, none of these formats have become true interchange formats, even though some them can be used to exchange musical as well as notational (e.g. graphical) information between applications and/or operating systems. However, we nd that existing representations are either too weak to encode all the required information (like, for example, MIDI), or they are too complex (like, for example, SMDL). The recently developed music representation language GUIDO [Hoos et.al.; 1998a] is a new approach to music representation which is capable of transporting musical as well as graphical information. The basic idea behind the GUIDO design is representational adequacy which means that simple musical concepts are represented in a simple way and only complex notions require more complex representations. GUIDO is divided into three layers: Basic GUIDO covers simple musical and notational concepts; Advanced GUIDO supports exact formatting and layout speci cations as well as more advanced musical concepts; and Extended GUIDO provides support for musical concepts beyond conventional music notation. GUIDO is designed to be an open standard which can be easily extended to incorperate new musical concepts. It is currently supported by NoteAbility, a professional music notation program written by Keith Hamel [Hamel; 1997]; by the Salieri system, an interactive system for analysis, composition, and transformation of music on a score-level basis [Hoos et.al.; 1998b]; and by Elody, a compositional system based on lambda calculus [Orlarey et.al.; 1997]. Other musical applications supporting GUIDO are currently being developed; there are also plans for realising GUIDO support for OpenMusic [Assayag et.al.; 1997]. For a given piece of music, the GUIDO NoteServer transforms a GUIDO Music Notation (GMN) description into a graphical score. The output is either a bitmap-like format supported by all WEB-browsers (like GIF or JPEG), or a postscript le for usage in conjunction with other software, like word processors or publishing applications. This approach is very exible, as it works su ciently fast to support interactive changes of musical material with almost instantaneous display of the results. Thus, the GUIDO NoteServer o ers dynamic notation of musical material in an adequate and easy-to-use way. There has been some previous work on supporting conventional music notation on the WEB. Earlier HTML-based formats for music description have the disadvantage of being too weak for encoding all the relevant notational information, while requiring to much overhead for representing simple musical information. Musical scores written in this fashion were neither intuitive to read nor easy to edit. The new