The UMSIC-Usability of Music for the Social Inclusion of Children project was established as an IT collaborative project funded by the FP7 program by EC for 2008-2011. UMSIC is developing the JamMo (jamming mobile), a time-and place-independent system that provides an interactive environment for musical creativity in order to promote social inclusion of young children aged 3-12. JamMo is intended to all children but especially children who are at high risk of marginalization: i) children with social, attention or emotional disorders and ii) children with newly immigrant status. JamMo applications have been designed to have an easy access to the technology children are familiar with. Since now, JamMo for 3-6 and 7-12 singing and composition games have been implemented and qualitatively evaluated in target groups both in UK and Finland. In this paper we focus on the development of JamMo singing game application for 3-6 aged children. We aim first to describe the pedagogical and technical framework of the game. By highlighting the child-centered approach we concentrate to the design of the game both theoretically and by the participatory design method that was applied in working with children aged 5-6 in the early childhood context. In describing the participatory process in practice and the gathering the research data in Finnish nurseries during 2009-2010, the iterative nature of the work will be especially noted. Finally we discuss on the importance of the child-centered approach in game development in general and open some future perspectives for the JamMo.