Radio receives little critical attention. Of the various methods for communicating ideas and emotions—books, newspapers, visual art, music, film, television, the Web—radio may be the least discussed, debated, understood. This is likely because it serves largely as a transmission device, a way to take other art forms (songs, sermons) and spread them out into the world. Its other uses can be fairly pedestrian too: ball games and repetitive, if remarkably effective, right-wing commercial talk radio. Rush Limbaugh is the radio ratings champ; according to the industry’s trade journal he reaches 14.25 million listeners in an average week. Sean Hannity, working the same turf, trails him slightly.

But an equally large audience turns to the part of the dial where public radio in its various forms can be found. Public radio claims at least 5 percent of the radio market. National Public Radio’s flagship news programs, Morning Edition and All Things Considered, featuring news and commentary alongside in-depth reports and stories that can stretch over twenty minutes—are the second- and third-most-popular radio programs in the country, each drawing about 13 million unique listeners in the course of the week. These NPR shows have far larger audiences than the news on cable television; indeed, all four television broadcast networks combined only draw twice as large an audience for their evening newscasts. Morning Edition and All Things Considered are supplemented by well-regarded programs like The World, a BBC coproduction with Boston’s WGBH, and the business broadcast Marketplace—programming produced outside of NPR itself but within the larger world of public radio. In polls, public radio is rated as the most trusted source of news in the nation. The audience for most of its programs dwarfs the number of subscribers to the The New York Times or The New Yorker, or the number of people who read even the biggest best sellers.

About one in ten Americans tune in to public radio each week; if you landed in a spaceship someplace in America searching for thoughtful and nonpartisan culture, your first stop would be the public radio stations that usually show up below 92 on the FM dial. You’d find not just the big news shows but also a variety of call-in shows: national ones, like On Point, The Diane Rehm Show, or Talk of the Nation, with its much-loved Science Friday edition, but also a number of superb local talk programs, with hosts like Leonard Lopate and Brian Lehrer in New York, Michael Krasny in San Francisco, Steve Scher in Seattle, Larry Mantle in L.A.—the list is very long.

These differ from the commercial right-wing shows in that they daily feature guests from a wide spectrum of American political and cultural life: on the morning I’m writing this, for instance, Tom Ashbrook…