The constraints system within PWGL, PWGLConstraints, allows us to write rules using a special pattern-matching language. Typically, the assignments use as a starting point a score prepared with the help of Expressive Notation Package (ENP).
In this talk we briefly present the PWGLConstraints system along with some extensions that allow us to integrate more closely the textual rule descriptions and the information contained in a musical score.
Firstly, we present a work in progress called VIVO (VIsual VOice-leading) that allows us to visually define harmonic progressions and voice-leading rules. VIVO comprises of a compiler and a collection of visualization devices. ENP is used to build a user-interface that, with the help of common practice notation, allows to visually define harmony and voice-leading rules according to a simple protocol. These visualizations are converted to textual rules by the VIVO compiler, and, finally, the musical output is generated using these rules.
Secondly, we have developed an extension which allows us to access information from the score using our pattern-matching language. ENP provides a library of standard and user-definable expressions called ENP-expressions. They range from standard articulation markings (such as staccatos and slurs) to fully interactive multi-purpose graphical expressions (such as breakpoint functions). The new syntax allows us to retrieve during the search process information about and contained by the expressions. This information can then be used to guide the search in several different ways, such as, letting the melodic contour follow the shape of a graphical object.