It can be fun to create shared playlists on streaming music services -- it's a window into your friends' tastes. You don't necessarily want to wade through an app to add tracks, though, and they usually shut out pals who can't use the service. That's where Spotify thinks it can save the day. It's launching a Group Playlists chat extension in Facebook Messenger that lets anyone in a chat add songs to the queue, even if they're not using Spotify. Once someone has started one of these collective playlists, you just have to tap a button to start adding tracks.