Musical and computational structures present several parallelisms, such as sequences, loops, and triggered events. Because of these parallelisms, it has long been suggested that coding music could be a good way for young children to engage in and learn about computer science (CS). Despite these suggestions, coding music has not reached a widespread audience of young children, and the approach's potential to engage them has not been thoroughly demonstrated. We reasoned that a barrier to adoption is the conceptual complexity of imperative programming, which is the type of programming written as sequential lines of code.  In contrast to imperative programming, flow-based programming (FBP) is written as blocks connected by arrows, thus providing a more intuitive visualization of the computational (and musical!) structures. To evaluate the potential of FBP for engaging young children in CS activities, we created Mflow, a browser-based FBP platform that allows children to easily create sound compositions and play with sound structures. We developed a Mflow standards-aligned curriculum that teachers applied in their fourth-grade classrooms. Surveys indicate that children were greatly engaged, the experience successfully exposed them to CS, and increased their self-efficacy toward programming. Thus, FBP and Mflow appear as promising approaches for reaching a large number of children in the formal school system, increasing their exposure to and engagement with CS.