Technology begets wonders, such as radio talk show host Brian Wilson, who, thanks to satellites and the Internet, sits on his farm north of Baltimore and talks California politics with listeners on San Francisco's KSFO. Wilson wakes each day, fires up his Web browser and reads the morning San Francisco Chronicle online for the latest news from clear across the country. He's so good that his listeners could be forgiven for thinking that he's in the City by the Bay rather than in a bedroom in Maryland. This is what passes for local radio these days.

Satellites and digital recording also make it possible for oldies deejay Tom Kelly to finish up his afternoon air shift on WBIG in Rockville, then sit down in front of a microphone and record his next job, as JJ Jackson, the overnight oldies jock on KQQL in Minneapolis. And no one's the wiser -- except, of course, Clear Channel Communications Inc., which owns both stations. You do have to give Clear Channel a hand for this wink and nudge on the KQQL Web site: "Actually, JJ is perhaps the most 'there' overnight presence in Twin Cities FM radio."

Deregulation in the media industries begets wonders, too, producing not only deejays with multiple personalities, but multiple stations with single corporate identities. Ever since Congress eased limits on media ownership in 1996, companies such as Clear Channel and Viacom Inc. have gobbled up hundreds of radio stations, threatening diversity. In many cities, a single company controls a majority of radio advertising revenue and makes most of the programming decisions. Since 1996, Clear Channel alone went from 40 stations to more than 1,200; add the company's prominence in the concert promotion and outdoor advertising businesses and you have unprecedented influence on the nation's popular music.

The combination of technological change and freedom from government regulation has not liberated owners to do more with less; rather, companies have lunged at the chance to do far less and rake in much more.

Come June 2, the Federal Communications Commission (FCC) is expected to approve new rules that would allow even more consolidation in the media: TV networks would be permitted to buy more stations than they are now, a media company would be allowed to own as many as three TV stations in one city, and restrictions on cross-ownership between newspapers and broadcast stations would be lifted.

After an expected binge of station and network sales, companies with the deepest pockets could assert control over a region's major radio stations, cable TV system, Internet service providers, a couple of TV stations and perhaps the local paper, too. Synergy, that much-lampooned dream of 1990s media boosters, could finally happen in a big way, with one company providing news and entertainment via all media from a single newsroom. The result would hardly be a boon to newsgathering; rather, it would result in diminished public service.

FCC Chairman Michael Powell and other champions of further deregulation have taken the infinite capacity of the Internet as rationale for scrapping much of the remaining regulation of the airwaves. Does the FCC need to worry about media diversity when technology now lets any Jane Q. Citizen get on the Web and blog to her heart's content?

In a word, yes. The 1990s-boom-era rhetoric has come up empty, and Powell knows it. Despite the infinite promise of the Internet, cable TV, digital and satellite radio and whatever other marvels may lie ahead, the reality of corporate consolidation has been a serious diminution in the variety of opinions, news reports, musical choices and cultural offerings in both the commercial and public media. Greater concentration of ownership in TV would reinforce a remarkable oligopoly in which five companies -- Viacom/CBS, Disney/ABC, NBC, AOL Time Warner and News Corp./Fox -- boast 75 percent of primetime TV viewers.

The test case for consolidation has been radio. Ever since the 1996 easing of restrictions on ownership, big media companies have faced off against musicians, activists and some of the few remaining mom and pop station owners. The media companies say the airwaves offer a more bountiful selection of artistic riches than ever before and that they have brought big-city talent to backwater communities, replacing farm reports, swap shops and amateurish deejays.

But listeners hear the nation's broadcasters pressing the culture to its lowest common denominator in a cynical money grab. Rush Limbaugh, Howard Stern and Tom Joyner are piped into your hometown by satellite.

The big companies do offer variety -- of a sort. In Washington, Clear Channel introduced a new format, Jam'n Oldies, featuring disco and danceable R&B of the 1970s; the station flopped, but executives say that sort of innovation wouldn't have happened unless one firm had eight outlets in one city to experiment with.

But in the past few years, Washington listeners have lost far more music choices than they have gained, on both commercial and public radio: standards (WGAY, the only station in the market that aimed at older listeners, tried a series of failed formats); jazz (WDCU was sold to C-SPAN, which uses the frequency as a prototype of a satellite-delivered national audio service); bluegrass (WAMU dropped much of its local music programming to serve up more news and talk produced for a national audience); and classical (WETA dropped some daily music offerings to simulcast news programs already heard on WAMU).

In city after city, Clear Channel points to formats it has added -- hip-hop here, alternative rock there. But critics contend that even when the big companies add program formats, the music they play is the same old stuff. A study by the Future of Music Coalition, a Washington-based artists group, found that different formats feature almost identical playlists, sharing as much as 76 percent of the songs they play.

More important, the radio chain -- saddled with $8 billion in debt from its '90s acquisition spree -- has cut costs and increased ad rates to squeeze operating profits from its stations. The chain has replaced local deejays and news announcers with jocks who sit in Phoenix or Denver and record shows for stations thousands of miles away, tossing in a few local references for verisimilitude ("Hey, tough day on I-10! How about those Bucs!"). News operations have been eliminated or outsourced. And programming that once mirrored local standards now takes on the coarseness of New York and Los Angeles, where stunningly vulgar sex talk wins big ratings.

If deregulation was supposed to let a thousand flowers bloom, most of the garden appears to be in Clear Channel's yard. The company is regularly accused of limiting playlists, favoring artists who tour through the company's concert wing. (Clear Channel denies any connection between its concert operations and airplay.)

But so what? How many listeners know or care that their favorite pop or rap station is owned by a huge Texas conglomerate? So what if the deejay is talking about Richmond but sitting in Arizona?

"The fact is we're now a healthier industry and you have more choices," says Alfred Liggins III, chief executive of Radio One, the Lanham-based company that started with Washington's black talk station, WOL, and grew into the nation's largest minority-owned radio company. "Is it tougher for the little guy, the mom and pop owner? Yeah. But that little guy could not provide the same level of talent and service. There aren't 10 Jay Lenos. Why wouldn't you leverage such a talent? Technology allows you to do it, so why wouldn't you?"

But there is a downside to diluting the localism that has given radio its distinctive edge since the dawn of the Top 40 era in the 1950s. Radio for decades played a crucial role in building community -- from deejays visiting high schools to run record hops to news departments that provided essential coverage of storms, riots, elections and scholastic sports.

Consolidation and cutbacks in local staffing have eliminated many of those functions. The prime example wielded against the industry stems from an accident last year in Minot, N.D., where Clear Channel owns all six commercial stations. When a train derailment in the middle of the night released a frightening cloud of anhydrous ammonia, Minot police sought to notify the citizenry of the crisis. They called KCJB, the station designated as the local emergency broadcaster, but no one was home; the station was being run by computer, automatically passing along Clear Channel programming from another city.

Clear Channel argues that only a technical glitch prevented word from getting through. But glitches aside, the six stations now have only one news employee among them.

Even in Washington, where Clear Channel's stations do offer news headlines and WRC relays the audio of CNN Headline News, there is not one reporter gathering news on the street. When the planes struck on 9/11, several of Washington's FM stations had nowhere to turn but to TV; they merely fed the sound from those newscasts.

Maybe it's true that listeners neither notice nor mind. In a Pew Center for the People and the Press survey earlier this year, slightly more Americans said letting companies own more stations would make no difference than said such a move would have a negative impact. But radio executives know that listeners don't pay close attention to the source of what they hear, and that has freed the industry to economize on virtually every detail of programming. Traffic announcers on most big-city stations can often be heard on several stations in the same city, using different names or tones of voice to keep listeners from noticing. For example, Beverly Farmer, who's delivered traffic reports under her own name on several D.C.-area radio stations, has also done stints as "Alex Richards" on WMZQ, "Vera Bruptly" on WJFK and "Ginny Bridges" and "Lee McKenzie" on other stations.

That showbiz stunt is one thing for traffic reports -- what difference does it make who tells you that I-95 is jammed at the Mixing Bowl? -- but it raises tougher questions when it comes to news coverage. Yet the nation's largest traffic reporting company, Metro Networks (owned by a division of Viacom, one of the largest media conglomerates), is trying to win the job of handling news coverage for hundreds of music stations. With rare exceptions such as all-news stations in big cities, radio news has been entirely outsourced, and largely to one company. Even in Washington, it is rare for any radio reporter to show up at news events other than those from all-news WTOP, talk WMAL or occasionally public radio's WAMU.

Washington is a big enough market that its stations still provide hours of locally originated programming. But some popular programs no longer have much local content: WKYS's popular morning man, Russ Parr, used to joke about Hyattsville and comment on the shenanigans of the District government; now that his program is fed to stations around the country, the humor is more generic, the content less local. The same is true of Don and Mike, the bad boys of WJFK's evening drive-time show; Don Geronimo still growls about Fairfax traffic from time to time, but both hosts now spice their show with plenty of references to Philadelphia and other cities where their syndicated program also airs.

Again, listeners don't complain, but the lack of complaint is hardly an endorsement. Radio listenership has been in decline for years. Surely the emotional connection to radio that was a crucial part of the identity of the generation that tucked transistor radios under the pillow and graduated to stereo systems in time for the alternative rock revolution is all but gone. And while local character has declined, the commercial load has crept up to as much as 24 minutes an hour on some stations.

As I work on a book on radio's evolution over the past half-century, I hear almost daily from radio executives who lament what has become of their business and complain about how hard it is to offer creative programming when managers must run four stations at once and deejays are required to be inoffensive and unnoticeable. Even within Clear Channel, station executives privately bemoan what artists now loudly protest, a system in which big radio takes advantage of its market power by requiring record companies to pay for their songs to be on the radio.

In his recent song "The Last DJ," Tom Petty sings, " . . . there goes your freedom of choice/There goes the last human voice/There goes the last DJ."

But the arguments against further consolidating ownership of the media are not simply nostalgia for a time when deejays served as guides to cultural shifts.

There is also a powerful rational objection to a new wave of consolidation, one that fits the FCC's penchant for justifying policy decisions with economic and legal argument: The enormous debt and cost-cutting that follow corporate consolidation has produced a need for safe, bland and cheap programming -- and declining consumer interest. Chain ownership has diminished both the diversity and vibrancy of discussion and debate -- and that is what the FCC is charged to protect on the public's airwaves. As Justice Louis Brandeis once said, "We can have a democratic society or we can have the concentration of great wealth in the hands of the few. We cannot have both." Marc Fisher is a columnist for The Washington Post's Metro section. He is working on a book about radio's evolution since the advent of TV.