Audio routers are patching writ large.
Audio routers are “virtual cables” that route audio out of limited parochial software into differently limited parochial software, giving you flexibility at the cost of confusion and labour. Using audio effects software to apply effects audio synthesis software doesn't sound like rocket science, but turns out to be tedious.
There are 5 that I am aware of, with different reliability, licensing, and platform support.
- jack (open source, Windows, OSX, Linux, powerful but unfriendly)
- loopback (commercial, OSX)
- soundflower (free, OSX, flakey)
- VB Audio Cables (donationware windows)
- Audiobus, the iOs router, which I have no use for at present.
Breaking it down by platform:
Jack on OSX has its only working version hidden deep in the github bug reports as opposed to the normal download page, indicating that development on this project has partially stalled. Soundflower is inflexible and periodically unmaintained despite intermittent commercial backing. Fragility hell in these free options is avoided somewhat by loopback, a rather expensive commercial competitor which is maintained, but AFAICT doesn't have the flexibility of Soundflower as far as routing audio from an app back to the app as with external apps, and seems to only do stereo. Maybe owners Rogue Amoeba will use that funding to keep maintaining their product, having fucked up soundflower on their own watch? But should I reward that behaviour by buying a license?
Apparently I did.
See linux audio hell. JackAss routes midi from jack-blind hosts:
JackAss is a VST plugin that provides JACK-MIDI support for VST hosts. Simply load the plugin in your favourite host to get a JACK-MIDI port. Each new plugin instance creates a new MIDI port.
Jack seems to work on windows. But there is also… VB Audio Cables seems to be a viable workalike for windows.