Yes, you can use your Rane TTM 57SL with MixEmergency. You just need to plug in your TTM 57SL, start up Scratch Live (and don't enable/push the Video-SL button), and then start up MixEmergency. There are some controls that aren't available in MixEmergency (such as using the buttons and knobs to select transitions/effects), but the main controls, such as faders will be set up to work as default (though you will have to activate the little buttons below the upfaders in MixEmergency if you wish to link them to the TTM 57SL's upfaders).
