The latest version of Spotify for Linux contains a new “feature”: At the start of every track, a little notification with track info is shown. I am on Kubuntu 14 and at least here it renders as a popup. It is really annoying, and the Spotify developers were not kind enough to add an option for turning it off in the GUI.
Here is how to turn off the track notifications until Spotify adds a checkbox in the GUI:
Turn off Spotify.
~/.config/spotify/Users/YOUR_SPOTIFY_USER_NAME-user/prefsin a text editor.
Add the setting
ui.track_notifications_enabled=false. Save the file. Done.