PWSynth: A Lisp-based Bridge between Computer Assisted Composition and Sound Synthesis

Symposium:


Session Title:

  • UNESCO Session: Music

Presentation Title:

  • PWSynth: A Lisp-based Bridge between Computer Assisted Composition and Sound Synthesis

Presenter(s):



Abstract:

  • This paper introduces a new Lisp based software synthesizer called PWSynth. In simple cases PWSynth can be used like other visual synthesis languages with the help graphical patches. The main aim with this project is, however, to integrate sound synthesis with a novel music notation package. This scheme allows to control sound synthesis interactively with a familiar representation of complex musical information. The system has also proven to be useful when designing different control strategies for physical models of acoustical instruments.

    Introduction and Background

    Computer music software has been divided in the past roughly in two main categories: computer assisted composition and sound synthesis. The former category (PatchWork, Laurson 1996; Open Music, Assayag et al. 1999) consists of systems that are typically built on top of a high level programming languages – for instance Lisp – and are meant to be used as non-real-time environments. The main emphasis has been in representing and generating musical material for instrumental music. The latter category consists of real-time sound synthesis environments (e.g. SuperCollider2, McCartney 1998) where performance is of primary importance. This has led to systems that do not include extensive tools for representing complex musical entities.
    During recent years the distinction between these two approaches has become more obscure. On the one hand SuperCollider2 has built-in tools that allow the user to specify compositional structures. On the other hand PatchWork contains user-libraries – such as PWCollider (Laurson 1999c) – which are meant to serve as bridges between non-real-time compositional work and real-time environments. Although the latter approach has made it possible to work in both domains, the idea of interfacing two systems with different logic and syntax causes several problems.
    PWSynth is a PatchWork user-library that aims at a better integration of computer assisted composition and sound synthesis. PWSynth is a part of a project which investigates different control strategies for physical models of acoustical instruments. PatchWork is used to generate control data from an extended score representation system called Expressive Notation Package or ENP (Laurson 1999b; Kuuskankare and Laurson 2000). The actual synthesis was meant to be realized with a synthesis environment outside PatchWork (either with MSP or SuperCollider2). This approach, however, turned out not to be fruitful. It became obvious that we need better integration of the high-level aspects and the DSP parts of the system.
    The rest of this paper is divided in four main sections. First we discuss in general terms ENP and describe how it can be used for sound synthesis control. After this we go over to PWSynth starting with the basic structure of the system and extending it to cover more complex cases that are needed when designing model-based instruments. The next section gives some ideas how ENP and PWSynth are interfaced and how ENP is used to control the synthesis engine. We end with a concluding section and give some ideas for future work.

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