OK, that’s a longer story 
In Ableton Live I have the scenes.
Each scene is for a song, so no need to load different Live Sets.
In Ableton I am using a M4L Patch wich reacts on incoming OSC messages to locate the desired scene and fire it.
Also the levels of the backing tracks are controlled by incoming OSC messages.
In GP when a rackspace is switched an OSC message is sent to Ableton to locate the desired scene.
When the Play button on my S88 is pressed, the global play in GP is started and again an OSC message is sent to Ableton to fire the selected scene.
As LINK is enabled in Ableton Live and GP the tempo of both is automatically set to the tempo of the scene in Ableton Live.
When I press the stop button on my S88 the global play is stopped in GP and so is stopped in Ableton.
Take a look at this thread, I uploaded a sample gig and the M4L patch