MIDI to Audio (Mopho synthesizer)

[typhy]

I have a Mopho Keyboard synthesizer and it is connected to my Macbook via USB. I would use midi cables but the midi ports on my interface are already occupied. I'm having trouble getting audio from the midi tracks. I don't know what I am doing wrong.. this is how I got it set up:

Midi Track:
Input - Mopho Keyboard "all channels"
Output - Interface

Aux Track:
Input - Input 2 (where the Mopho is connected)
Output - free Bus channel named "Synth"

Audio Track:
Input - Bus channel "Synth"
Output - Main outs

I'm confused as to why I'm not hearing the synth when playing back.

[filosofem]

On M-Audio Venom when used as an audio interface (ASIO) Venom Vyzex Editor has a button Record USB. Does Mopho have a similar option? If not a more traditional approach is probably needed where you would use 1/4 inch TRS cables OUT of Mopho to Interface IN.