This turned out to be ridiculously easy.
My first real-deal DJ controller was a used Numark Mixtrack Pro II that worked 99% perfectly, despite looking a little scuffed. Eventually I got a Pioneer DDJ-REV1 that I use as my main deck now, with the Mixtrack as a spare just in case.
A couple weeks ago, I had an idea. See, the DDJ-REV1 has the capability to do 4 channels by hitting a button to swap between channels 1/3 on the left and 2/4 on the right. However, that’s not ideal, and given I already had to write a lot of the control mapping for it in Mixxx (Mixxx doesn’t include a mapping for the DDJ-REV1), I didn’t want to deal with that doing that for two more channels. But I did have the Mixtrack and a riser.
So now my setup consists of the DDJ-REV1 on the desk, with the Mixtrack Pro II on the riser above it, both connected to the PC via USB and the speakers connected to the DDJ-REV1.
The unexpectedly easy part was modifying the mapping for the Mixtrack Pro II.
It was literally a find-and-replace in Notepad. Everywhere “CHANNEL 1” occurs, replace with “CHANNEL 3.” Everywhere “CHANNEL 2” occurs, replace with “CHANNEL 4.”
That’s it.
There are still a few things I need to run through in terms of making sure all of the rest of the controls are mapped properly, but I would’ve had to do that anyway. The Mixtrack Pro II’s mapping in Mixxx is good, but it’s far from perfect. Good enough, however, to be usable as decks 3 and 4 without much more work!
Now to learn 4-channel mixing and get used to the new setup with a VR headset on.