It's conventional chattering-class wisdom to say that Terry Gross of Fresh Air is a "great interviewer." In the early days I think that wisdom originated to some significant extent in male-listener fascination with the sound of her voice. But a broadcast I just heard was not only a reminder that she is, in fact, truly a great interviewer but also a demonstration of what that means in practice.

The broadcast in question was her 43-minute session yesterday with Ayers, the person presented by GOP campaigners as Barack Obama's closest and most influential friend. Ayers himself came across, inevitably, as a more complex character than the campaign caricature: more sympathetic in some ways, not necessarily in others. But much of what Ayers "reveals" comes out precisely because of the way Gross posed and sequenced the questions. If he had just been parked in front of the microphone by someone who said, "Well, how can you hold your head up?" or "So, tell us about Barack Obama," the results would have been much duller.

At the most obvious level, Terry Gross succeeds in this interview simply by avoiding the two most common, and laziest, styles of today's broadcast interviewers: surplus aggressiveness, long ago made familiar by Mike Wallace and now lampooned by Stephen Colbert;  and lapdogism, most recently on display in Greta Van Susteren's sessions with Sarah Palin and the default mode of Larry King Live. Both of these extremes reflect the confusion of toughness of manner --  do you interrupt, are you scowling, are you borderline impolite -- with toughness of inquiry, which is something altogether different and can happen under the most polite and civil auspices.

She also avoids the common pitfall of highbrow public broadcasting-style interviewers: giving in to the temptation to show off how much she knows and how smart she is in the set-up to the questions.

What she does instead, and what she shows brilliantly in this interview, is: she listens, and she thinks. In my experience, 99% of the difference between a good interviewer (or a good panel moderator) and a bad one lies in what that person is doing while the interviewee talks. If the interviewer is mainly using that time to move down to the next item on the question list, the result will be terrible. But if the interviewer is listening, then he or she is in position to pick up leads ("Now, that's an intriguing idea, tell us more about..."), to look for interesting tensions ("You used to say X, but now it sounds like..."), to sum up and give shape to what the subject has said ("It sounds as if you're suggesting..."). And, having paid the interviewee the respect of actually listening to the comments, the interviewer is also positioned to ask truly tough questions without having to bluster or insult.

If you have this standard in mind -- is the interviewer really listening? and thinking? -- you will be shocked to see how rarely broadcast and on-stage figures do very much of either. But listen to this session by Gross to see how the thing should be done.