It started out as a hobby: host your own laidback audio show out of the basement, Wayne's World-style, then make it available to Internet users for listening on their digital media players. All you needed was a cheap microphone, something to say and time to kill.

But last month, the grassroots phenomenon known as ''podcasting'' went mainstream. Apple Computer made the talk or music shows, known as ''podcasts,'' easier to find and download on its iTunes online music store. The site went from zero podcast subscriptions to more than a million in just two days.

Corporate media moved quickly to stake out podcasting as an avenue for reaching new listeners. While early podcasters offered talk-radio-style shows with quirky titles such as The Frat Pack Tribute and The Rock and Roll Geek Show, big companies have elbowed in with condensed versions of popular broadcasts. Now, it's Queer Eye Hip Tips and ABC News that dominate as the most popular podcasts on iTunes, making the one-person, in-house shows harder to spot in a sea of media logos.

The result demonstrates how a new technology can remain part of an underground culture only for so long before corporations adopt it. Indie podcasters say Apple's decision has brought them new listeners, but they complain that the iTunes Web site heavily promotes big-name podcasts while leaving out their homegrown shows.

``We invented podcasting,'' said Todd Cochrane, who hosts his own podcast, Geek News Central out of his home in Honolulu. ``The people who are coming in now are jumping over the fence and joining the party. It's funny how Apple is so focused on the commercial shows and how little they are emphasizing the grassroots side of podcasting.''

Podcasting, coined by joining the word ``broadcasting'' with the Apple iPod digital music player, is generally credited to former MTV video jockey Adam Curry and software developer Dave Winer, who created some of the key software and popularized the idea beginning last year. Subscriptions to podcasts are free to listeners.

The concept works like this: anyone who wants to rant or discuss a topic can record and post an audio file on the Internet. Listeners can use software to subscribe to the show, getting an automatic update every time a new installment is recorded. Then they carry the show around on a portable music player - an iPod or similar device - and can listen to it anywhere.

Now, with Apple's newest software release, those who download podcasts from the iTunes Web site can more easily transfer the audio files directly to their iPods.

The move widens the range of listening content available on the Web site and allows Apple to further promote the iPod as the king of digital media players.

It's logical for Apple to emphasize corporate media podcasts over just any amateur with a show because big names are more credible to listeners who are new to the phenomenon, said Alex Nesbitt, who runs Digital Podcast, an online directory of 2,100 podcasts.

``Getting people to try the media is the first step,'' he said.

More people are trying podcasts, even the indie ones. Cochrane's technology talk show drew 7,000 to 8,000 listeners per podcast before it became available on iTunes. Now, about 10,000 people tune in to the show twice a week, he said.

But Cochrane said he thinks that big-name podcasts from CNN and Walt Disney take away from the whole reason people started doing it in the first place: to talk comfortably and informally to what is sometimes just a handful of loyal fans.

``I think what's so novel about it is that it's your neighbor creating this content,'' Cochrane said. ``It's the person across the street.''

It's not clear that there is a mass audience for podcasting, or whether the phenomenon could turn out to be a fad.

Broadcasters see podcasting as a way to reach new listeners. These days, people want the freedom to listen to audio files whenever they feel like it, rather than on the strict schedule of a traditional radio station, said Phil Redo, vice president of station operations and strategy for New York public radio station WNYC.

``We have got to be in those spaces or we run the risk of becoming less relevant to them,'' Redo said.

In January 2005, WNYC posted its first podcast on its Web site and added three more in March. Before they became available through iTunes, the shows generated about 86,000 downloads a week. Lately, that number has exceeded 125,000.

``It catapults us into a mainstream environment that we otherwise wouldn't get,'' Redo said.

In the Internet age, there is room in the public eye for both corporate media shows and basement podcasts, just as there's an audience for both mainstream news and Web logs, or blogs, said Lee Rainie, director of the Pew Internet and American Life Project.

``There will always be hits driving the media, but the new thing that has entered the culture is that the small niche markets have found their own place,'' Rainie said.

The addition of podcasts to the mainstream iTunes Web site was the equivalent of putting podcasting ``on steroids,'' introducing it to the masses and enticing new listeners, he said. The effect on podcasts, both corporate and indie, was like ``Ed Sullivan putting your act on his show,'' Rainie said.

Besides, many podcasters do it just for fun and don't seem to care if they have a widespread audience. ``They have things to say,'' Rainie said. ``If it turns out that their six friends and their mother listen to them, that's enough.''

Indie podcasters themselves scoffed at the idea of losing their loyal listeners, asserting that any hardcore devotees they have would not fall for the corporate media podcasts that have taken over the iTunes Web page.