Has anyone sucessfully used the Yamaha KX61 and the Yamaha Audiogram 6 controllers together using Cubase AI4 ? I have both units and I’d like to use them @ the same time if that’s possible. Mostly to record a Drum track, Synth pad track & live Bass guitar & Vocal. I’m very new to AI4 and Laptop recording in general. (I’m used to stand alone Analog/Digital multitrack.) Advice would be helpful I think. 
Don’t see why not, remember that the Audiogram 6 can only record and playback two channels at the same time!
Also the KX61 usb interface is for MIDI and the control of Cubase and will not produce sound VIA the USB, you will need to connect the line outs (KX61) to the Audiogram and monitor from the line outs of the Audiogram once you have selected the correct audio driver in Cubase.
IIRC the KX61 is MIDI only and does not have any audio inputs or outputs.
This shouldn’t be a problem though, I use a Korg Microkey alongside my Tascam US144 to do much the same things as you want to, both devices work fine side by side.
Ah yes, so it is. Oops