This thesis draws on a video ethnography of music activities in a preschool setting in Sweden. It focuses on the participants’ co-construction of music activities and on their use of semiotic and material resources to constitute and sustain these activities. The videos document musicking (Small, 1998), that is, events involving a series of musical activities: work with instruments, dancing and movements, singing and listening. The data were collected during one year and includes 24 hours of video films (altogether 30 musicking events). The participants in the study are 1-3 years old children and their music pedagogues (preschool staff members who worked in the preschool on a daily basis). In terms of theoretical influence, the study is inspired by conversation analysis (Sacks, 1992), linguistic anthropology and work on aesthetic processes (Duranti & Black, 2012; Sawyer, 1997; 2003), as well as sociocultural theorizing (Lave, 1996; Rogoff, 1995; Wenger, 1998). The findings show that the individual young children (2-year-olds) engage in musicking, and that they also initiative various novel activities: such as conducting, dancing, singing, and exploring instruments. In these activities, mobility in the room is essential for the children`s access to instruments and other artifacts and for their possibility to participate in specific activities. The musicking events evolve as multimodal events, where different participation strategies are allowed and creative improvisations involve both musical and extra-musical actions. But a major finding is that the music pedagogues’ responsive uptake and creative improvisations are critical for the individual children`s ability to participate in specific activities and for bringing together the individual child and the group in collaborative musicking. / Forskarskolan: Globalisering, literacy och utforskande lärprocesser: Förskolebarns språk, läsande, skrivande och matematiserande (GUL).