This paper presents a web-based application enabling audiences to collaboratively contribute to the creative process during live music performances. The system aims at enhancing audience engagement and creating new forms of live music experiences. Interaction between audience and performers is made possible through a client/server architecture enabling bidirectional communication of creative data. Audience members can vote for pre-determined musical attributes using a smartphone-friendly and cross-platform web application. The system gathers audience members’ votes and provide feedback through visualisations that can be tailored for specific needs. In order to support multiple performers and large audiences, automatic audience-to-performer groupings are handled by the application. The framework was applied to support live interactive musical improvisations where creative roles are shared amongst audience and performers (Open Symphony). Qualitative analyses of user surveys highlighted very positive feedback related to themes such as engagement and creativity and also identified further design challenges around audience sense of control and latency.