Heres an easy way, up in the top right corner of ableton is the midi map and key map buttons you can push the key map buton click the red (arm record activate) button at the bottom of you midi chanel and press a key on your computer kybrd (like 1,2,3 and so on) to map it two then repeat with your other midi chanels to other keys, once different keys are maped to different chanels you can activate each chanel with each button. Press multiple keys at the same time to activate multiple chanels at once. It will play all active chanels with each note you hit on your midi controller and will also allow you to layer the virus with other synths and plugins as well. Sorry I ve been tied up with work and havent had a chance to get back to your pm but I will.
