My main interface is a Focusrite Scarlett.  This has been working fine for a long time. 
 
I am getting ready for a session where I will be recording a piano and flute.  I recently bought a Yamaha MX88.  That has a USB interface, supported by the Steinberg generic driver.
 
I am able to record MIDI from the piano over that USB interface.  I would like to also record the audio.  I know I can simply run TRS jumpers from the piano to spare channels on the Scarlett, and that is my default plan.  I spent some time experimenting to see if I could get the audio to come directly across the USB driver.
 
I actually can do that in Cubase -- but in that case, I cannot send the DAW output to the Scarlett.  I suppose there is some way to set up the "control room" function on Cubase.  I was planning to do this session with Cakewalk anyway because I am more comfortable with the take lanes.
 
When I pull up the preferences under Cakewalk for audio driver, all the Scarlett interfaces are selected as usual.  The Steinberg driver shows up, but it is greyed out.  I can't find any way to make that active.
 
Any ideas?

As far as I know  a Pc can only handle one asio device. Maybe in the future???

fitzj
As far as I know  a Pc can only handle one asio device. Maybe in the future???

And I guess that is why Cubase stopped playing to the Scarlett.  After I installed the driver, the next time I started Cubase, it popped up a box allowing me to select the Steinberg ASIO driver.
 
So I'll drop back to plan B and run the MX88 audio into a pair of Scarlett ports.
 
Now I have to figure out how to get Cubase to stop using that Steinberg driver and switch back to my Scarlett driver.  Always an adventure.

I used to use my Tascam us1641 along side a Yamaha mixer that used the Stienberg USB driver. I would simply switch to WDM mode while recording the band. I think WASAPI will also work.
 
Just be aware that you may need to pay attention to timing offset if your overdubbing to existing tracks. . ASIO is normally dead on, but all other modes can be out of sync. 

You can use Dante to do this.
 
I was looking into this myself to exactly the same thing, but haven't had the time to research further.
 
The idea is that you register both your hardware ASIO devices as Dante devices on your local network, then use the Dante Virtual Soundcard as your main ASIO device. You can also use ASIO drivers on other PC's or Mac's and stream over your network.
 
The lowest latency you'll get is 4ms though, and I'm not sure if this is including or on top of your hardware's latency.
 
This setup would probably require the Via / Virtual Sound Card combo at US $59.95.  You can get a 14 day free trial to try it out.
 
If you do give it a go, please let me know if you have any joy with this.

sock monkey
I used to use my Tascam us1641 along side a Yamaha mixer that used the Stienberg USB driver. I would simply switch to WDM mode while recording the band. I think WASAPI will also work.
 
Just be aware that you may need to pay attention to timing offset if your overdubbing to existing tracks. . ASIO is normally dead on, but all other modes can be out of sync. 

sock monkey
I used to use my Tascam us1641 along side a Yamaha mixer that used the Stienberg USB driver. I would simply switch to WDM mode while recording the band. I think WASAPI will also work.
 
Just be aware that you may need to pay attention to timing offset if your overdubbing to existing tracks. . ASIO is normally dead on, but all other modes can be out of sync. 

AFAIK if you want to use two digital interfaces under WDM (I assume WASAPI would be the same) You need to establish one of them as the digital clock master, and slave the other. You need a physical hardware connection for it. This is best done if both units have a wordclock connection, but I believe that an S/PDIF cable may work too. 

I've used 2 interfaces using WDM mode and as Sock Monkey say's it works without issue for live sessions were you need more inputs. I never had to sync or use wordclock. The tracks all lined up perfectly in this case because they are all recorded at the same time.
 But WDM, WASAPI and worst of all MME mode are always off snyc when attempting overdubs so you need to switch back to ASIO and only use one interface. This works great for capturing a live band or drums and then adding other parts later in ASIO.
Below shows a typical attempt at overdubbing and what happens in each mode.

 
If you do need to use WASAPI or WDM mode for overdubs you can fix the issue using manual offset. You'll need to perform a loopback test to see how much you need to enter in the box. Or you can simply nudge the tracks into sync.

Cactus Music
 But WDM, WASAPI and worst of all MME mode are always off snyc when attempting overdubs so you need to switch back to ASIO and only use one interface.

Once again, this image simply illustrates the need to apply the correct Record Latency Adjustment manual offset ...nothing more. Once configured properly any record mode will sync up just fine.

Synchronization is only an issue when there is overlap between audio channels on two separate interfaces. For example, if you had two microphones on a guitar cabinet with each one plugged into a different interface, you'd want both devices clocked from the same source. But any individual source is not going to be bothered.

Yes, the timing issue with using mulltiple different audio interfaces is not what the image in msg #7 shows. The timing issue with multiple interfaces is a clock issue, the image is a driver issue.