Ok, Let’s try to take things one after the other…
- If you have defined your Ketron keyboard as an external instrument, it should appear as so in the External Instrument pane of your Studio > Audio Connections window. Could you make a screenshot of it?
- Once the external instrument is defined, the best to do is to set it as an instrument rack (Add rack instrument… command in the contextual menu of the right zone, VSTi pane) in the project. You should be able to select your Ketron in the Steinberg > External plug-ins catagory of the available instruments list. This will immediatly create a subfolder dedicated to your Ketron in the VST instruments one. Additionaly, you 'll probably be asked to create a MIDI track for it.
- After this, nothing prevents you from adding as much MIDI tracks as MIDI channels needed with, for each of them, the Output routing set to your Ketron vie the relevent MIDI port, only the MIDI output channels being different one from the other (I guess that you have a bi-directional MIDI connection between your DAW and the Ketron keyboard).
At this stage, you should be able to record all what is MIDI related.
After this, recording the related audio is a matter of creating all the needed tracks, with their input routing set accordingly to the audio outputs of your keyboard and set them as ‘Record enable’ before starting the record, the MIDI tracks playing in the background. This is the more ‘primitive’ way to do so.
Another way (available only with the Pro version of Cubase, I think) is to use a ‘dummy’ bus to be able to record directly both MIDI and audio signals coming from your keyboard. Here is the way to proceed : what works for the multitimbral sampler used in this example, works also for an external instrument, as they are both set as rack instruments (in the VST instruments folder) in the project.
Beside this, forget the Render in place command when dealing with external instruments : we have to record them in real time, as they are existing devices for which the real world time can’t be stretched, contrarily to virtual computing objects.
HTWH…