Following a computational approach to music creation can serve as a transdisciplinary bridge between computer science and music, providing rich opportunities for teaching computing skills in interdisciplinary contexts. Making use of such learning contexts is one of the cornerstones of STEAM (STEM + Arts) education, a pedagogic approach focusing on integrating the arts and humanities into STEM fields. Despite numerous benefits reported in the literature, the number of STEAM programs integrated into formal learning contexts remains limited due to various integration challenges. In addressing these challenges, we developed and evaluated a gamified music computing learning application called muco, using the MVC software architecture along with React as the front-end, and Node and MariaDB as back-end technologies. The goal of the application is to make programming concepts more accessible and comprehensible to a broader public, and to simultaneously spark interest in music and music making. Making use of game mechanics, muco is conceptualised to teach computational thinking, and more specifically, introductory programming, in non-formal learning contexts. The usability of the application and impact of interdisciplinary learning is evaluated by means of both formative and summative testing. Results suggest that the application provides an engaging learning environment which encourages the exploration of both the computing and music domain.