[CentOS] USB audio on Centos-7

> (and a possibly separate issue: how the heck does one point Audacity
> to a USB input? Can't find anything in its UI, and there's darn little
> help online that is actually helpful, in this regard.)

Not sure about the other stuff but my USB dock's mic input shows up in
Audacity on Fedora 26 under the second drop down on the last row (next
to the little microphone icon).

In the passed I've had most luck with pavucontrol, since it was the
only one I could find that would allow me to turn on monitoring.