In this article for BBC Music Magazine‘s May 2016 issue, I look at the success and growing pains of Groupmuse, an online service that facilitates house parties featuring chamber music performances. Groupmuse is one of a growing number of “sharing economy” startups (like Uber and Airbnb) that allow users to monetize their goods and services via websites and mobile apps. But can it sustain its aggressive growth plans without more revenue sources?