Hi Joseph, The "Link to Crossfader" button affects the MIDI mapped control too. The generaly idea is that you would MIDI map the crossfader of your S4 to the crossfader of MixEmergency. When that button is enabled, the S4 will be able to control the crossfader of MixEmergency. When disabled, it won't. This can be useful for certain situations, such as when you want to cut/scratch and not affect the video, or use a different mode of crossfading (autofade, upfaders, etc). The "Bass" effect mode works only with Serato's software. You can however use the "Grid" mode if you send MIDI Clock from Traktor, and enable the MIDI Clock option in MixEmergency (you'll find it if you go to the menu-bar -> Window -> MIDI). Once you do this, all of the functions in MixEmergency that react to the Beat/Grid will follow the MIDI Clock sent from Traktor. I believe that this would be the easiest way to achieve what you want to do. As for sending controls through to Quartz Composer, it depends what you want to send. It would be possible to map, for example, the output level meters from Traktor, to an input of the Quartz Composition - that's a slightly more advanced thing to do though, so it might be best to get the Grid/Clock method working first.
