How did you do that? In detail.My input is a mono mic.
If I select the internal mic on my Macbook Pro and stereo on the Audacity drop-down tool bar, Audacity will record that mono microphone in two-track.
I think you can do that trick with a mono USB microphone, too. If you're using an external mixer and enter the Mac via the stereo analog input, I think you're stuck with left-only or mono. I need to check that when morning actually comes.