A Constraint Based Approach to Musical Textures and Instrumental Writing

PatchWork (PW), (Laurson, 1996a), is a visual programming language which has a direct correspondence to its base languages Common Lisp and CLOS. The user operates with graphical entities (boxes) and defines relations between them with the help of connections. PW has been extended by several user libraries that are designed to solve specific musical problems. Our focus in this paper is a user library called PWConstraints (Laurson 1996a and 1996b). In PWConstraints the user does not formulate stepwise algorithms but describes the desired result with a set of rules. This approach has been used to solve concrete large-scale musical problems. During the last years PWConstraints has been extended to cover other areas such as generation of rhythms, textures and expressions. This paper offers also some new ideas how instrumental writing could be incorporated more deeply in the computer aided composition process.