This article describes two rather different and innovative systems that allow multiple users to evolve sound collaboratively. The Sound Gallery was conceived as an interactive installation artwork where the movements of a group of physically present participants are tracked over time and influence the evolution of sound-modifying hardware circuits. AudioServe is a tool that allows visitors to a web-based interface to evolve sounds by mutating virtual frequency and amplitude (FM/AM) modulation circuits left on the server by previous users. The two projects eventually became linked when the physical interface system designed for the Sound Gallery was connected to an adapted version of the audio-synthesis engine built for AudioServe . The two systems are described, the techniques used to create them are explained and some of the issues involved in collaborative sound evolution are discussed.