@Seamus OReally asked me about this when the MixBus sales was on, and I'll give you all the full answer, because there are old videos on YouTube that make it sound as if you can mix an LPX project on MixBus for free, in a ReWire type of arrangement. Actually, if you're running macOS 10.15 or later, you can't. Here's why. First off, Harrison doesn't support ReWire, so there goes the easy option. Secondly, OS 10.15 was the first to drop 32-bit support completely. As no-one has developed 64-bit versions of the free audio routing utilities Soundflower and Jack, neither of them will work. (Soundflower looks as if it will, until you try to actually set it up...) There is one utility that appears promising – iShowU – but really it's for desktop streamers, and it doesn't have the multitrack I/O capabilities you need. Suffice to say, if you're running OS 10.14 or earlier, Jack and Soundflower are still options. That's because the OS has 32-bit support. If not, there is only one option I can find: Rogue Amoeba's Loopback https://rogueamoeba.com/loopback/ The Catch 22 is, even if Loopback does the job, it costs a lot more than MixBus. That makes it all a bit pointless. On the plus side, if you want to mix on MixBus, it supports VST plug-ins, so you probably already have all your 3rd-party plug-ins available in that format. Then, all you have to do is import your WAV files from LPX. My guess is you won't bother, but the option is there.