Until recently, the sonification of Virtual Environments had often been reduced to its simplest expression. Too often soundscapes and background music are predetermined, repetitive and somewhat predictable. Yet, there is room for more complex and interesting sonification schemes that can improve the sensation of presence in a Virtual Environment. In this paper we propose a system that automatically generates original background music in real-time called VR-RoBoser. As a test case we present the application of VR-RoBoser to a dynamic avatar that explores its environment. We show that the musical events are directly and continuously generated and influenced by the behavior of the avatar in three-dimensional virtual space, generating a context dependent sonification. 371374Juslin, P.N., Sloboda, J.A., (2001) Music and Emotion: Theory and Research, , Oxford University Press, OxfordNew YorkMeyer, L.B., (1961) Emotion and Meaning in Music, , University Of Chicago PressGilkey, R.H., Weisenberger, J.M., The sense of presence for the suddenly-deafened adult: Implications for virtual environments (1995) Presence, 4, pp. 357-363http://www.iasig.org/Guy, W., Design with Music in Mind: A Guide to Adaptive Audio for Game Designers, , http://www.gamasutra.orgSinger, E., Feddersen, J., Redmon, C., Bowen, B., LEMUR's musical robots Proceedings of the 2004 Conference on New Interfaces for Musical Expression, , Hamamatsu, JapanCamurri, A., Mazzarino, B., Volpe, G., (2003) Analysis of Expressive Gesture: The EyesWeb Expressive Gesture Processing Library.Manzolli, J., Verschure, P.F.M.J., Roboser: A real-world composition system (2005) Comput.Music J., 29, pp. 55-74Wassermann, K., Eng, K., Verschure, P.F.M.J., Live soundscape composition based on synthetic emotions (2003) IEEE Multimedia, 10, pp. 82-90Wanderley, M.M., Schnell, N., Rovan, J.B., ESCHER - Modeling and performing composed instruments in realtime IEEE Int. Conference on Systems Man and Cybernetics, , San Diego - CA, USARowe, R., (1992) Interactive Music Systems: Machine Listening and Composing, , MIT Press, Cambridge, MA, USATorque Game Engine, , http://www.garagegames.comK. Team, K-Team Corporation. Lausanne, SwitzerlandBernardet, U., Blanchard, M., Verschure, P.F.M.J., IQR: A distributed system for real-time real-world neuronal simulation (2002) Neurocomputing, 44-46, pp. 1043-1048http://www.puredata.orgVerschure, P.F.M.J., Voegtlin, T., Douglas, R.J., Environmentally mediated synergy between perception and behaviour in mobile robots (2003) Nature, 425, pp. 620-624