I am just confirming that the CP73 is not really an audio interface that will use the extra audio inputs to connect an external synth and connect to DAW?
The inputs are just like a pass through. I have been trying to setup for a long time with Logic and have just figured this out.
The CP has a real audio interface for itself. What you are trying to understand is the nature of the input. It is not an A/D Input. This means it does not convert the audio connected to it from analog-to-digital. It is simply an audio input that feeds the analog audio output.
Therefore, unlike the MODX/MONTAGE which have an A/D Input — audio connected to an A/D Input is converted from analog-to-digital signal, that signal can then be processed with on board Effect processing and sent to the “TO HOST” USB connection where you can record it to your DAW.
The CPs feature a simple Audio In, no A/D conversion.
That said, the CP’s own sound is converted to digital and can be recorded to your DAW via USB “TO HOST”.