JACK Audio Connection Kit
If you know anything about JACK, please expand this article. I've uninstalled it, so I can't really expand it any further.
Multiprocessor implementation (soon: JACK2)
Here's a mp version of JACK which will also be used as base for JACK2. However, I couldn't figure out how to use it - if you do, please edit the wiki.
Alternatively, there is the normal version from the extra repository, install it with:
pacman -S jack-audio-connection-kit