Is it possible for me to use the Yamaha Steinberg driver for the MODX in conjunction with the Focusrite, or is that impossible?

It is not natively possible to have two audio interfaces active at the same time in Windows. The "natively" qualifier means that you can add additional 3rd-party layers (3rd Party to either Focusrite, Yamaha, Steinberg, or Microsoft) that can allow for running multiple audio interfaces at the same time. The 3rd party solutions will add latency to your audio chain - so there will be a performance impact. The degree of this impact is partly CPU/memory bound (how "beefy" your computer is) and partly bound to the OS internals and/or implementation of the 3rd party driver and how it interacts with the others.

You can make it work about the same as you can make your foot fit into shoes that are a bit small. Squeeze/pull hard enough and you can claim your feet are in those shoes. At the end of the day - your feet hurt and you may decide ultimately to just get bigger shoes (... change your requirement/approach).

Mac natively supports aggregate audio devices - so that environment supports this kind of setup a bit more officially. Under Windows you would need to use ASIO4All or VoiceMeeter (or similar product from the same company) to allow for "combining" audio interfaces.

There may be a breakdown by introducing these layers in what exactly is supported or how things operate (or don't).

It's not necessarily the wrong tree - but not far from it.

Although inconvenient - the best approach would be to cable up your MODX when you need the independent audio channels to/from MODX and then disconnect and wire up your Focusrite when you need that audio interface to do whatever job you use it for.

"Disconnect" and "rewire" could be simply picking one or the other interface within Cubase. There may be other things you want to switch around ("rewire" ) at that time.

Thanks, I kind of figured that would be the answer. Was hoping it wouldn't be, though.

I kind of thought I'd be able to simply choose Stereo Out 1: MODX/Yamaha/Steinberg OR Stereo Out 2: Focusrite.
Alas, Focusrite is the only option.

Just as an additional point to consider. A computer-based studio is very much like any standard recording studio in that it can be reconfigured for the task at hand. This may mean disconnecting and reconnecting audio devices to your studio monitors. Logistically, this can be troublesome (but can be overcome).... Cubase allows “hot swapping” (changing ASIO devices, mid session, without having to shut down the project to do so). A feature you will come to appreciate.

Depending on your workflow (which can vary greatly) — consider the order in which you construct your session. If, for example, you work bottom up... where you record the music tracks first, then overdub sweeting, then melody and vocals added later. In this type of workflow you would use the MODX as audio interface to record the music (synth) tracks — using freely MIDI and Audio recording to construct them. This would use the Yamaha Steinberg USB Driver as the ASIO device. You would wind up with rendered Audio Tracks of all the MODX parts.

Next, you could move to adding things that would require a Mic pre-amp with phantom power, etc., For this portion of the session, you would need to reconfigure.

When working with audio overdubs, reconfigure the studio around the Focusrite as audio interface, connecting it to your monitor speakers; using its recommended driver. As long as you work at a consistent sample resolution, you’ll have no problem playing back the rendered MODX audio tracks via the Focusrite. At that point it is simply computer audio sent to the Focusrite to be converted to analog for the monitors.

What I am suggesting is don’t simply pass on this. The advantage in all the swapping of audio interfaces is clear: you can take full advantage of the 10 USB Audio bus Outputs of the MODX when laying down the synth music tracks, and take advantage of othe Audio Interface when needed.

If, however, you are looking for one setup configuration that can accommodate everything you’ll be doing, or you are in a situation where you are recording multiple musicians, simultaneously — then, naturally, you’d want to have everything running in one configuration all together. And as pointed out... that is not going to happen easily.

These are not unusual situations. Although some times it is a logistical nightmare to reconfigure. I have to constantly reconfigure, because I need to test and verify all manner of combinations of gear. So I know it can be done, when necessary / and I also know that it can be quite painful some times.

Yes, Bad Mister, that ability to switch is very nice. After I posted my question yesterday I flipped to the Yamaha driver and plugged headphones into the MODX so I could play along with audio tracks. I plan to cable the MODX to the Focusrite as Jason suggested.

I had a pipe dream where the MODX audio stream would get to Cubase via the Yamaha driver, then Cubase would output everything vis the Focusrite.

That was stinkin' thinkin'. 😀

I looked at the software ASIO mixer software Jason mentioned but I'm not sure I want to get into that.

I dismantled my studio 10 years ago to go work in a cubicle. Getting back into it is very interesting. So much has changed.