In relation to children’s musical understanding it becomes meaningful to create material and environments fit for exploring, composing and playing with notes. The aim of the study is to examine and analyse a legocomposing project, set in a pre-school environment through an intra- active perspective. The intra-active perspective, musicking, music related agency and the building blocks of music become this studies theoretical resources. The project was conducted during the course of four weeks, with thirteen five-year-olds.The content that appears in intra-activity between agents revolves around the building blocks of music and the relationship between note value and pulse. Learning through music becomes primary, when the children explore, problematize and create meaning through their musical process. The children become different in themselves through intra-activity with Lego, they become legocomposers, music researchers and soundpainters. In this way Lego can be understood as a performative agent. The empirical material, which was generated by video observations, can be divided into two themes. One where the children in intra-activity compose with Lego and one where the process starts in music and then translates into Lego. The result show that the pre-school teacher acts front-player more often when the process starts in music.