Working with popular street cultures in the Global South offers scope for practice-based research (PBR) to go beyond its application with creative practitioners in the galleries and theatres of the Global North. We start from an account of a “reasoning session” with reggae sound system owners, selectors, and engineers staged as a PBR event in Kingston, Jamaica. Such popular music cultures across the Global South have their own specialist apparatus for playing recorded music and—most important for a PBR investigation—their own embodied, situated, and tacit knowledge systems. These include the sophisticated arts of selecting music, tuning up a sound system, and the value of the culture for the communities from which they originate, as well as strategies for current challenges, such as police harassment and lack of government recognition or support. Accessing such grassroots knowledge systems requires not only a good rapport with local practitioners but also close cooperation with their own organizations and with local university researchers. Such PBR also demands sharing research findings—for example, by screening the documentary film we made of the reasoning session for its participant. It is concluded that practitioners’ ways of knowing as revealed by PBR can help challenge conventional ideas about the nature of knowledge itself.