I am using Gig Performer and Ableton Live.
OSC must be enabled in Gig Performer.
To synch both I created a M4L Patch and a small script.
When a rackspace is activated the corresponding Ableton Live scene is selected.
When the global play is activated the current selected scene is started.
When the global play is deactivated the play in Ableton Live is stopped.
Link must be enabled in Ableton Live and Gig Performer for the global play working fine.
Just load the attached Max Instrument Select_Scene_GP into a Midi Track.
In the GP script the IP-Address 127.0.0.1 is used (Gig Performer and Ableton Live run on the same machine).
You could change this IP-Address so it would be possible that Gig Performer and Ableton Live run on different machines in the same network.