With the recent wave of development in Virtual Reality (VR) technology, new purposes have been found for the medium. The complex motion tracking and limitless environments allows for interesting new ways of interacting with musical instruments. Recently, researchers have examined the concept of musical interaction in VR, which has led us to a new category in expressive musical interfaces; Virtual Reality Musical Instruments (VRMI). The thesis project presents interactive prototypes with integrated physics-based sound synthesis through an iterative design process of usability and crossmodal association evaluation. The main conclusion of the usability evaluation includes further improvements to the robustness between gesture mapping and collision detection system. From the crossmodal association experiments, a slight tendency towards successful identification of size and material of the sound producing object was found, however, given the small sample size and potential flaws in the experimental design, future work and evaluation remains a requirement for raising the validity of the indicative tendencies.