This paper discusses several compositions that use the computer screen to present music notation to performers. Three of these compositions, Law of Fives (2015), Polytera II (2016), and Terraformation (2016–17), employ strategies that allow the notation to change during the performance of the work as the product of composer-regulated algorithmic generation and performer interaction. New methodologies, implemented using Cycling74's Max software, facilitate performance of these works by allowing effective control of generation and on-screen display of notation; these include an application called VizScore, which delivers notation and conducts through it in real-time, and a development environment for real-time notation using the Bach extensions and graphical overlays around them. These tools support a concept of cartographic composition, in which a composer maps a range of potential behaviors that are mediated by human or algorithmic systems or some combination of the two. Notational variation in performance relies on computer algorithms that can both generate novel ideas and be subject to formal plans designed by the composer. This requires a broader discussion of the underlying algorithms and control mechanisms in the context of algorithmic art in general. Terraformation, for viola and computer, uses a model of the performer's physical actions to constrain the algorithmic generation of musical material displayed in on-screen notation. The resulting action-based on-screen notation system combines common practice notation with fingerboard tablature, color gradients, and abstract graphics. This hybrid model of dynamic notation puts unconventional demands on the performer; implications of this new performance practice are addressed, including behaviors, challenges, and freedoms of real-time notation.