I spent some time trying to get Audacity to work under Kubuntu — I kept getting a "check audio output device" error during playback. Finally, I stumbled across this in the ubuntu forum and am reposting it here in order to post it in as many places as possible. It works like a charm:

1. Install JACK Control (might have to use Add/Remove; I did not)
2. Start Jack Control; click Setup.
3. On the Misc tab, select Start JACK audio server on application startup, then click OK
4. Open Audacity
5. In Audacity, select JACK Audio Connection Kit: system as the output device

Now to see about Rezound, Muse, and Hydrogen.