Over the past few centuries, classical music making has evolved to be centrally and hierarchically organized. Centralized music offers less autonomy/agency to musicians, thus putting some limitations on their creative expression. Attempts to decentralize music making, however, are met with substantial challenges, in terms of coordination and collective decision making. In this research, we propose to develop new technology to address the challenge of decentralized music organization. Specifically, we will design an online platform, called Music on a Whim (MOAW), that enables amateur musicians to organize ephemeral ensembles in a decentralized way, by making collective decisions about goals/purpose (what the music making is for), groupings (who plays with whom) and curriculum (what to play), and in collaboration with professional musicians, composers, teachers and artists from other domains.