Let me take a different approach.

The Kurzweil is a synth module. It doesn't have a controller built-in. I could hook up a cheap Casio to it and get it to work. That's not how I'll be using it. The "controller" I'll be using is the DAW sending midi to the Kurz.

What comes out of the Kurz is analog audio (and almost always--if not always) in stereo. I could hook speakers up directly to the Kurz and get sound. That's not what I intend to do, however. I want to send the analog audio back to the computer/DAW to be recorded on another track. Of course, somewhere along that chain it will have to be digitized.

I am sure the Kurz can also send/pass midi signal to another device...including the computer/DAW. But that's not what I want to do. I want to get the audio it's sending digitized and back to the DAW.

So is a USB/Audio interface with Midi I/O essential? What's going to go "in"? Analog Audio or Midi? If it's analog Audio, can I be sure it's stereo?

I think Mario's broad suggestion/understanding is the way I'll go, though I may spring for a brand-name interface. It's not going to break me. But I will consider an Audio/USB interface with midi I/O if that will indeed get Analog Stereo from the synth back to the DAW in one step.

BIAB 2021 Audiophile. Windows 10 64bit. Songwriter, lyricist, composer(?) loving all styles. Some pre-BIAB music from Farfetched Tangmo Band's first CD. https://alonetone.com/tangmo/playlists/close-to-the-ground