Since Symfonium support many providers and renderers it often have to start a service to manage all that.
Google have decided that services must provide a notification so that the users knows something is going on. Unfortunately most users do not want to know. The good news is that you can hide them.
Open the status bar shade.
Long press the notification or swipe it to the right depending on your OS version.
Select turn off notification or click the settings button.
Turn off background tasks and Download manager notification if wanted. You might want to keep the normal Symfonium notification as it drives many things include Wear support.