In this presentation we will show how the ImprovisationBuilder framework was adapted to our compositions for pianists and computers. Software design issues include: capturing, transforming, and realizing MIDI piano data, and an easy-to-use graphical interface for altering parameters during performance. Compositional issues include: the causal responsorial aspect of the ImprovisationBuilder output, and varying the small-scale event and gestural levels while preserving the large-scale structure among multiple performances. The presentation will discuss the compositional and performance importance of these issues and show how each of these issues was handled within the ImprovisationBuilder framework. Work on this project suggests the advantages of addressing compositional and software design issues simultaneously and cooperatively. Both composer and software designer can benefit from this collaboration.