Designing the computer-based interactive opera Virtualis has led the authors to develop new tools for working with music, especially in three-dimensional spaces designed for representing and manipulating it, as well as an interaction model based on physical forces rather than on the user's intentions. Although opera and computing are two dissimilar interactive situations, the software environment presented in this article is intended (1) to combine them through the generalization of certain operatic functional relationships and (2) to offset the relative absence of the spectator from the classical performance of drama.