This article reports on a study which investigated the spontaneous instrumental music-making of three- and four-year-olds in typical pre-school educational settings in London, UK. It argues that many prior studies of children's music-making have analysed and evaluated such activity against models drawn from the practices of Western art music and its conventions of analytical theory, and suggests that this approach has certain drawbacks. The study adopted a grounded theory methodology moving through three phases in different nursery classrooms. Each phase was characterised by successive focusing and refinement of methodological tools in response to the emerging findings. Data were collected on videotape which was then repeatedly reviewed, transcribed and categorised. The children's music-making was analysed as relational processes in time and space involving the two-way interplay of child and instrument. Structures in space delineate the child's movement within the spatial potentials and constraints of the instrument design. Structures in time describe how movements and movement ideas were strung together in ever-lengthening portions.