Is it possible to record audio-responsive Quartz compositions along with the audio?
Well, you can import the audio into quartz or play it through the mic input using Soundflower.  http://quartzcomposer.com/plugins/1-export-to-movie SHOULD export it. Then you can go back and add and line up the music to the video with iMovie (or something better) and export it.

*Soundflower Instructions: Open soundflowerbed, in the menubar (top) a little flower will appear, click on it and go under "Soundflower (2ch)" and click "Built-in output." This will let you hear the audio when you do this. Then go to your system preferences, go to audio settings, and change the OUTPUT to "Soundflower (2ch)" When you go into Quartz Composer, drag the Audio Input (if you have not already) and wire it up. Then go to settings in the inspector and check "Select a specific audio source" and select "Soundcloud (2ch)." Then go and play whatever you want on your computer.