Much of music learning happens outside the classroom in an informal setting, for example online by watching YouTube movies. Despite the many research effort and government projects, many online lack pedagogical foundations while few music educators fully employ online technology yet. In this paper, existing research on online music learning is reviewed as well as platforms and sites that are currently available, mapped in a so-called “market quadrant”. Also, the main problems with the current state-of-the-art are identified, along promising technologies that are believed to address these challenges.