We propose a music generation software that allowslarge numbers of users to collaborate. In a virtual world,groups of users generate music simultaneously at differentplaces in a room. This can be realized using OpenAL soundsources. The generated musical pieces have to be modi-fiable while they are playing and all collaborating usersshould immediately see and hear the results of such mod-ifications. We are testing these concepts within Croquet byimplementing a software called Jam Tomorrow.