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This article provides an overview of our free Lispbased, cross-platform, visual programming environment called PWGL (the name is an acronym for PatchWork Graphical Language). PWGL can be used for computer-aided composition, music analysis, and sound synthesis. Our work is influenced by our past experience with PatchWork (Laurson 1996; Assayag et al. 1999). However, PWGL has been completely rewritten and redesigned in our attempt to develop and improve many of the useful concepts behind PatchWork. PWGL and several of its applications have already been discussed in our previous work, including Laurson and Kuuskankare (2002, 2006), Kuuskankare and Laurson (2006), and Laurson, Norilo, and Kuuskankare (2005). Since 2002, PWGL has undergone several revisions and additions including the public release, launching of the PWGL home page, inclusion of the tutorials and new programming interfaces, etc.; each of these have been attempts to make our system more available and more easily approachable within the computer music community. The main purpose of the present article is to give a general overview of the current state of the system with an emphasis on features that are useful for potential PWGL users, such as composers, music analysts, and researchers. PWGL is programmed ANSI Common Lisp (Steele 1990) from LispWorks (www.lispworks.com), which is source-code compatible across several different operating systems, such as Macintosh OS X, Microsoft Windows, and Linux. LispWorks provides support for Foreign Language Interfaces, by which a program written in one programming language can call routines or make use of services written in another. LispWorks also supports the OpenGL graphics library API. (The graphics part

At present, there are a large number of commercial and free programs dealing with music notation. Two of the most notable free software projects are LilyPond (Nienhuys and Nieuwenhuizen 2003) and Guido (Hoos et al. 1998; Renz 2002). Both of these programs are LaTeX-like languages that are used to describe the contents of a musical score in a textual form and not through a point-and-click user interface. Furthermore, a Web site dedicated to music notation software, ace.acadiau.ca/score/others.htm, lists a large number of other commercial and free music notation programs including simple notation editors (e.g., abc) for typesetting relatively simple notation; special-purpose editors like Gr6goire for typesetting Gregorian chant, Django for typesetting tabulature, and GOODFEEL for Braille notation; and full-featured programs like Berlioz, Igor (programmed in Lisp), Nightingale, and SCORE. Finally, the two de facto commercial notation programs are Finale and Sibelius. Recently, Web-viewable applications have also started to emerge. There are a few commercial approaches such as Scorch by Sibelius Software. ScoreSVG (Bays 2005), in turn, is a-free alternative based on the Scalable Vector Graphics, a language for describing two-dimensional vector graphics in XML. A handful of Lisp-based applications also exist that are aimed at representing musical data, such as Common Music Notation (CMN; Schottstaedt 1997), the Rhythm-Editor of PatchWork (RTM; Laurson 1996), and the musical editors in OpenMusic (Assayag et al. 1999). One of the earliest experiments, MUZACS (Kornfeld 1980), was even written for a Lisp machine. Of these editors, RTM is primarily intended to represent musical raw material, and thus the editing capabilities are limited. This is also the case with Open Music's notation editors. CMN is powerful typesetting package but lacks a graphical user interface (GUI). Expressive Notation Package (ENP; Kuuskankare and Laurson 2002) is a music notation program that has been developed to meet the requirements of computer-aided composition, music analysis, and synthesis control. ENP is programmed with LispWorks Common Lisp (www.lispworks.com). LispWorks, in turn, is a Lisp implementation that is source-code compatible across Windows, Linux, Mac OS X, and some UNIX platforms. ENP is primarily intended to represent Western musical notation roughly from the 17th century onward with a strong emphasis on modern notation. ENP is not a full-featured music typesetting program. However, it is designed to produce automatic, reasonable musical typesetting according to the common practices described, for example, in Stone (1980) and Read (1982). ENP is used as a notational front end in a visual programming language called PWGL (Laurson and Kuuskankare 2002). PWGL is a combination of several software packages build on top of Common Lisp. In addition to ENP, the components include, for example, a rule-based programming language called PWGLConstraints (Laurson 1996), and a sound-synthesis program called PWGLSynth (Laurson et al. 2005). The development of PWGL is focused toward the Mac OS X operating system, but it currently runs also under Windows XP. A Linux version is under consideration. PWGL is freeware, and it can be downloaded from our Web site at www.siba.fi/PWGL/. ENP has a sophisticated GUI based on direct editing, a rich set of musical primitives, an extended concept of expressions, and algorithmic control over scores. It contains a unique set of features that cannot be found elsewhere, at least to this extent of integration in one program. ENP allows one to analyze, modify, view, and annotate scores in many different ways; a text-based format can be used to generate scores algorithmically; it is possible to modify data contained by the objects in a score by using a scripting language; our rule-based programming language can be used Computer Music Journal, 30:4, pp. 67-79, Winter 2006 ? 2006 Massachusetts Institute of Technology.

Director Musices is a program that transforms notated scores into musical performances. It implements the performance rules emerging from research projects at the Royal Institute of Technology (KTH). Rules in the program model performance aspects such as phrasing, articulation, and intonation, and they operate on performance variables such as tone, inter-onset duration, amplitude, and pitch. By manipulating rule parameters, the user can act as a metaperformer controlling different features of the performance, leaving the technical execution to the computer. Different interpretations of the same piece can easily be obtained. Features of Director Musices include MIDI file input and output, rule palettes, graphical display of all performance variables (along with music notation), and user-defined performance rules. The program is implemented in Common Lisp and is available free as a stand-alone application both for Macintosh and Windows platforms. Further information, including music examples, publications, and the software itself, is located online at http:// www.speech.kth.se/music/performance/.

As the 1980s wore to an end, the wonderful PDP-10 and Samson box (Samson 1985) at the Center for Computer Research in Music and Acoustics (CCRMA) began to seem fatally old-fashioned. MIDI was everyone's new darling; tape music was dead. Worse, the old 1960s vintage hardware began to fall apart, and the repairs rivaled the designs of Rube Goldberg. When CCRMA decided to buy NeXT computers, it became painfully obvious how much we were losing-hundreds of thousands of lines of unportable Sail, Fail, and FORTRAN code, hundreds of years of effort, and the best FM synthesizer anywhere, all tossed into the trash heap. I had spent more than ten years building a little computer nest (Schottstaedt 1983) and, in the course of writing more than 20 pieces, had become very much at home there. The move to the NeXT set me back ten years with no straightforward way to recover my favorite instruments or composing tools. I had three choices: the NeXT MusicKit (Jaffe 1989), Csound (Vercoe 1991), or start all over from the beginnning. The NeXT MusicKit was similar to the Samson box system we had just left, and CSound was essentially the same as the old Mus10 world, an outgrowth of Music V (Mathews 1969; Pope 1993) that the Samson box software had replaced. Both of these choices were familiar, and both were in use by real composers, so I started out on the assumption that one or the other would become my new home. I tackled the MusicKit first. It provides a sophisticated entry into the NeXT sound-support hardware, including highly optimized access to the NeXT's built-in Motorola DSP56000, a 24-bit microprocessor aimed at common digital signal-processing tasks. Unfortunately, one DSP56000 is not a Samson box. It can just barely synthesize two FM violins (Schottstaedt 1977) in real time, but I was used to using as many as 50. To continue writing the kind of music I like to write, I would have to split up the note lists into 56000-size pieces, then do lots of overlays. In addition, the MusicKit's real-time orientation leads to complicated envelope and instrument definitions and makes it difficult to get at individual samples. Despite my admiration for the job David Jaffe and Julius Smith have done, the more I looked into the MusicKit, the less I seemed to be getting from it. On the other hand, Csound, which several of my friends use and regard very highly, did not run at that time on the NeXT, and my attempt to port it failed. So, I sat down to write yet another version of Music V.

Common Lisp (Steele 1990) and the Common Lisp Object System (Bobrow 1988) provide an environment uniquely suited to the exploratory and incremental process of musical composition. Common Music is a high-level music composition language built in Common Lisp and CLOS designed to support computer composition in a variety of score formats through a common protocol. Initially prototyped on a Symbolics Lisp machine, the system runs under most Common Lisp environments found on standard computers such as Apple Macintosh and NeXT machines. Common Music is currently offered at CCRMA as part of course work for computer music classes and workshops. It is available through anonymous file transfer (ftp) on the machine ccrma-ftp in the file named /pub/cm.tarfile.Z