Summerstage Rocks NYC

New York's rock clubs are being taken over this week by ... by what, exactly?

When it began, 25 years ago, this annual festival was called the College Radio Barnstorm, but it was soon renamed the CMJ Music Marathon (CMJ stands for College Media Journal). And what was once a gathering for college-radio D.J.'s has evolved into something a bit harder to define. More than 1,000 bands are converging on the city this week, and organizers expect the events, which started last night and continue through Saturday, to attract nearly 100,000 fans and professionals, some of whom might be wondering what they're doing here.

As in years past, the lineup of bands, especially indie-rock bands, is impressive. Well-established acts still show up at the marathon: the New Pornographers, for example, occupy the top spot on CMJ's college-radio chart; this exuberant (and somewhat cryptic) Canadian band is to play the Bowery Ballroom tonight. The room will fill up quickly. A CMJ pass, which costs as much as $445, does not guarantee admission. (A full schedule is at www.cmj.com.)

The marathon has a reputation for allowing professionals and amateurs to discover new music, though many of the bands have already been discovered. Some, like Against Me!, a rousing, roaring Florida punk band (Saturday night at Irving Plaza), have new albums to promote. Some, like the restless Canadian singer-songwriter Feist (she came to town for a Wednesday-night showcase at the Knitting Factory), have major-label contracts but not, in the United States, a major-label fan base. Some, like the playful but harsh noise-music group Nautical Almanac (tonight at the Hook in Brooklyn), are likely, and probably happy, to remain far underground. And many others are here because of managers or radio promotion people or booking agents or publicists, who all use these showcases to showcase themselves, too.