Learning how to actively theorise music is a complex process which is challenging to observe and describe for teachers, students and researchers. In this study, we explore the potential of a mixed-methods research design for understanding how theorising is developed and how the different methodological approaches used in the study can improve our understanding of precollege students’ experiences of learning to theorise music. The study combines (1) qualitative methods such as observation, analysis of video and audio recordings and interviews, (2) software development as music education research, (3) eye tracking and (4) musical analysis. We suggest that a considerable advantage of a mixed-methods approach is that it can make students’ thinking visible and audible. In addition, it can improve precision in identifying novelty and surprise during the learning process. Such moments of new musical conceptualisation are particularly important in a context of abundant access to many musical genres and styles.