Flow Moods: Recommending Music by Moods on Deezer

They allow users to discover new songs or artists they may like within large music catalogs, and they are known to improve the overall user experience on these services [5, 22]. In particular, the French music streaming service Deezer [7], offering 90 million music tracks to 16 million active users from 180 countries, extensively relies on its homemade Flow feature to recommend music. Flow materializes as a simple button, proposed to Deezer users on the homepage of the service. A click on this button launches a personalized and virtually infinite radio-style playlist of songs, computed internally using collaborative filtering methods [3, 16]. However, despite promising results over the past years, Flow used to ignore the moods of users when generating playlists.