Cloud services allow musicians and developers to build audience participation software with minimal network configuration for audience and no need for server-side development. In this paper we discuss how a cloud service supported the audience participation music performance, Crowd in C[loud], which enables audience participation on a large scale using the audience audience's smartphones. We present the detail of the cloud service technology and an analysis of the network transaction data regarding the performance. This helps us to understand the nature of cloud-based audience participation pieces based on the characteristics of a performance reality and provides cues about the technology's scalability.