via createdigitalmusic.com: A project that has been in the works for some time is now beginning to surface, Jack for the Windows Platform. If you’re not familiar with Jack - not making music on Linus, or you don’t need it on Mac - it’s a low-latency audio server for your music software: i.e. - a way to route the audio from one software program to another. If you use different software for different tasks, have stand-alone applications that you’d like to play in real-time rather than rendering/importing, you know how useful something like this could be.

Since this is a more or less open source matter, a lot of the technical information may take me a while to absorb. But from what I can tell, it is working, though still in early (?) development. There are graphical controllers for the Jack server: here & here. And if you have a multi-processor setup you’re golden. So if you’re at all inclined to hack your OS and really loosen the tyranny of closed systems, get in on this. And since I’m still playing catch up with the technical end of all this (I’m a little thick sometimes if you haven’t noticed), I’m not entirely clear whether it is able transmit MIDI as well. But on the CreateDigitalMusic thread the developer of the Jack API joined the comments to give some good insights into the workings of this project. Good stuff.

Also,

Another commenter pointed to LoopBe1 a virtual MIDI-driver that I wasn’t aware of. It appears to be a good alternative to MIDI-Ox/MIDI Yoke which, frankly, is looking a little long in the tooth. If I could just find a decent system MIDI monitor than I would be set.