A Web-based service that lets users stream songs to their computers or mobile devices.  Such services may let users download songs for offline playback as well as allow users to upload their own music collection to the cloud, the latter known as a "music locker."  See 
Spotify, 
Pandora, 
Napster, 
Google Play Music, 
YouTube Music, 
Apple Music, 
iTunes, 
iTunes Match and 
cloud music storage.