I am a big fan of the Awesome-Windows-Manager for Linux but since a couple of weeks the Spotify-Client is freezing the X-Server for couple of seconds after a track change happened.
I've already been thinking about that this has something to do with the track notification from spotify.
After some research I discovered the option
ui.track_notifications_enabled. After disabling the track notification, Spotify worked quite well again!
It can be used from the command line:
Or set in the configuration file (~/.config/spotify/Users/<spotify_login>-user/prefs):
(This was found on hackzine.org)