Yet with lightning speed, the quintet with the loopy name turned into this year's local act to watch. The five friends from Connecticut College—singer-songwriter Alec Ounsworth, 28; drummer Sean Greenhalgh, 27; keyboardist Robbie Guertin, 26; guitarist-keyboardist Lee Sargent, 28; and his twin brother, bassist Tyler Sargent—have sold more than 45,000 copies of their self-titled debut without so much as an indie label's backing. In fact, the outfit has spent much of the year rejecting bids from labels big and small, favoring a do-it-yourself path instead. And the musicians—all Brooklyn residents with the exception of Ounsworth, who commutes from Philadelphia—will end 2005 with a sold-out headlining gig at Irving Plaza on New Year's Eve, capping a rise resulting from a serendipitous collision of timing, Internet savvy and a pop tune's best friend: hype.

January–March
Clap Your Hands' year began auspiciously. Jasper Coolidge, a booker at Pianos, secured the band for a January residency at the fashionable Lower East Side space. "Jasper sent us an e-mail that said, '2005 is going to be huge for you,' " Guertin recalls. "We were psyched."

Coolidge says the e-mail was part of his plan to "build the band's confidence, like a football coach," in order to prepare the jittery musicians, whose "uncalculated" delivery he found refreshing. Already, the band had defined its sound with a rare meticulousness, pointing both to voguish '80s acts and '90s indie groups. Most striking was the contrast between the band—with its dueling keyboards and zealous chug—and the singer, strapped with a harmonica that gave him the air of some old blacklisted folkie, who onstage exuded all the enthusiasm of a teenager stuck in study hall.

The three nights marked a turning point for the band, though at first they hardly seemed earth-shattering. "There were about 80 to 100 people for each," Coolidge says. "We have a lot of nights where the room is far more packed. But the right people came: bloggers, press, industry." Indeed, the band got lucky: January is a sluggish month in which even the typically spoon-fed music media is forced to dig hard for ideas. By the end of the residency, Clap Your Hands had been written about in blogs such as Brooklyn Vegan and I Rock I Roll; in February, TONY previewed shows at Sin-é and Mercury Lounge, which had started booking the group in opening slots. "I began getting calls from friends," Greenhalgh says. "They'd say, 'So, you're doing something useful with your life!' " Clap Your Hands had also attracted a posse of guardian angels. These included not only Coolidge—an L.E.S. busybody who began funneling people to their shows—but Dave Godowsky, who managed the band in its formative stages. "We made a yearlong plan," Godowsky says. "But it all started going faster than we'd expected."

April–May
The group's local profile was rising, but its principal concern remained finishing the album it had started the previous June. When they concluded the mixing and mastering in the spring (all told, the recording cost the band $8,000), the members were faced with the two standard options: hitching their fortunes to a respected indie label, or signing to one of the major labels that were already sniffing around.

The musicians opted for a third alternative: bypassing the time-honored traditions—both arguably superfluous in an age when bands' websites function as worldwide merch tables—and releasing the album themselves. Ounsworth, who was paying the rent by renovating houses in Philly, says he was "just too impatient to try to impress these record-label people." The decision also came from Godowsky and Nick Stern, a friend of the band who'd taken the managerial reins in late spring (and who, like Godowsky, works by day as a music publicist). "I told the band if they wanted to go the traditional route, count me out," Stern says. "I was excited to map out a different way to make a band successful."

June–August
Clap Your Hands' self-titled debut was released the first week of June, with the band pressing 2,000 CDs. Because Tyler Sargent (who was working as a Web programmer) had the most room in his Park Slope apartment, he carried the brunt of the labor involved in distributing the record to both stores and Web customers. "I'd fill up a shopping cart with packages and roll it to the post office," he says. "The clerk would complain if there was, like, an incorrect sticker on the box. I'd think, Don't you people see what I'm trying to do here? "

On June 7, the band played a CD-release concert at the Delancey. "For us, it was just another show," Ounsworth says with his usual nonchalance. "We just happened to have albums. I remember playing, going home and going to sleep." Yet the first pressing soon vanished on the strength of the band's live shows, as well as Internet buzz. The influential Chicago website Pitchfork sealed their fortunes. With characteristic bravado, Pitchfork awarded the album 9 points out of a possible 10; orders came pouring in from outside New York. Insound, a Web catalog that had been selling the CD, saw an immediate spike. "Their record became the fastest seller we've ever had," says Matt Wishnow, the company's president.

The band began pressing CDs in quantities of 5,000, then 10,000. "It was essentially a demo," says Lee Sargent. "Nobody expected we'd be turning Tyler's apartment into a warehouse." Stern was contacted daily by interested labels; he batted them away like common phone solicitors. "We're not anti–record label," the manager says. "But why give somebody 80 percent of sales to do something we can do ourselves?"

September–December
The quintet planned a fall tour opening for the National, a seasoned band that could draw a crowd, and the musicians quit their day jobs before hitting the road. By the time the tour kicked off in September, however, Clap Your Hands' hype had eclipsed that of the headliner; throughout the tour, audience members would leave after the opening set.

In October, the band members obtained a distributor, ADA, to deal with the mounting orders (and, perhaps, Tyler Sargent's diminishing sanity). In November, the five toured Europe, where—confronted with the difficulties of infiltrating foreign markets—they signed to Wichita, the British home to acts like Bright Eyes and Bloc Party. Also that month, Ringo Starr plugged the group on his website. In December, Clap Your Hands performed on Late Night with Conan O'Brien, made plans to play Japan and prepared for their biggest concert yet: the New Year's Eve show at Irving Plaza. The National will open.

Whether Clap Your Hands Say Yeah would have benefited from more time in the incubator has yet to be determined. In an age of breakneck hype, it's worth remembering that the Beatles—who, despite what you may have read on the Internet, were a superior band to Clap Your Hands Say Yeah—spent years playing small clubs. "The speed of this," Stern admits, "is insane."

The propulsion causes the group anxiety—to a point. "You can't control people's reactions," Ounsworth says. "In the end, you just have to do your work. And hope it stands up."

Clap Your Hands Say Yeah plays Irving Plaza Saturday 31.