Of course, I just forward the song to the group chat in the Messages app, like any other thing I'd want to send to that group. If you have Spotify, however, you have a new group chat option to choose from: Spotify itself. As the admin, you have the power to add or remove anyone from the group chat. If you're in the group chat, you're labeled as a "Participant." The admin as well as any participants are allowed to block any group chat user for any reason.