How to capture whatever audio is playing

Moo0 claims to be able to do it, so does Audacity and SoundTap - but none of them do it for me. I start recording, then start the audio but they sit there 'waiting for audio stream.' The audio I'm trying to capture is coming from a Sonar plug in.

I only have one active sound driver (MOTU Traveler) and I'm using 'MOTU Audio Wave for 64 bit' for both recoding and playback. At first I thought that if these programs grab the audio at the onboard speaker outputs, that might account for it because I'm not using them, I'm using a pair of Traveler outputs instead. The problem with that theory is I can record sounds from the web without changing anything in the setup. Am I missing something simple?

Thanks - rev