Todd Moscowitz, president of Asylum Records, thought he might have a nice little novelty record on his hands when he first heard "Laffy Taffy," a playful song by the Atlanta rap group D4L. But the novelty has worn off. Now Moscowitz simply thinks of "Laffy Taffy" as a hit single. A very, very big hit single.

The song has been downloaded, both legally and for a fee, more than 700,000 times from iTunes, Yahoo! Music and other online outlets since its October release, according to Nielsen SoundScan. In the final week of 2005, "Laffy Taffy" (basically a lot of salty-sweet talk centered around a chant of "girl, shake that laffy taffy") shattered the one-week sales record for a digital single, with 175,000 copies sold. That's more than twice the previous mark set by Kanye West's "Gold Digger."

Commercially released singles, which were on the music industry's endangered-species list at the turn of the 21st century, have come roaring back to life in the digital age. In some ways, it's like the singles-driven 1950s and '60s all over again, with MP3s replacing 45s.

As iPods and other MP3 players outsell CD players, sales of downloaded singles are booming accordingly: Though sales of full-length albums were down 7.2 percent last year, the digital singles market grew by 150 percent, with 352.7 million individual songs sold online, Nielsen SoundScan reports. It was by far the highest figure for singles sales in any format since 1973, the first year for which Recording Industry Association of America shipment data are available for singles.

In December, weekly singles sales topped CD sales for the first time as U.S. consumers purchased 19.9 million digital tracks but just 16.8 million albums, according to Nielsen SoundScan.

To say nothing of the $600 million (and growing) ring tone business in the United States.

"Consumers, as has always been the case, love a hit single," says Charles Goldstuck, president of BMG North America, whose record labels include Arista, RCA, J and Jive, with best-selling artists from Jamie Foxx to Kelly Clarkson. "If it's a hit, people are willing to buy it now in greater numbers than they were ever before, principally due to the proliferation of distribution channels."

Says Geoff Mayfield, director of charts for the trade magazine Billboard, "We're seeing numbers that remind us a little bit of the heyday of the single."

The booming sales of digital singles, ring tones and digital videos offset some of the ongoing slump, in which various factors — from CD burning and illegal downloading to competition from other entertainment categories — have driven down annual album sales by more than 21 percent since 2000.

But the boom isn't an industrywide cure-all. Not with downloadable tracks selling for 99 cents on average, compared with the $18.98 of a full-length CD.

Thus the hand-wringing over the 2005 sales figures: Albums represented roughly 62 percent of all U.S. music sales and digital singles about 35 percent, according to Nielsen SoundScan; just three years earlier, albums accounted for over 90 percent of all U.S. music sales.

"Digital sales aren't growing fast enough to replace the losses in our traditional business," BMG's Goldstuck says. "The challenge for the industry is to find some balance between singles sales and album sales. We want to create an artist experience, not a singles experience."

Says artist manager Jim Guerinot, whose clients include pop singer Gwen Stefani and the rock bands Nine Inch Nails and Hot Hot Heat: "While somebody might view a scene from a play as being really well done, well performed and well written, most artists would prefer to have you watch the entire play. Musicians put their music out in a long-form format, complete with artwork, and their preference would be for you to experience their work that way."

Too, artists typically receive 14 to 24 cents on the dollar (or, rather, the 99 cents) in the sale of a digital single, but closer to $2 on the sale of a full-length album, Guerinot says.

"I'd rather sell a pack of gum than a stick of gum," he says. "I mean, you don't see Marlboro wheeling out single cigarettes in racks. They'd rather sell you the carton."

Lifehouse, a Southern California rock band, has sold 887,000 digital copies of its hit single "You and Me" — and just 770,000 copies of the album.

"There's really not that much money to be made on 99 cents," says Jason Wade, Lifehouse's singer, guitarist and songwriter. "It's better than nothing. It's better than people getting your song for free. But it's not big money. ... You even wind up losing some album sales, because if you have a hit single now, a lot of people will just download the one song instead of buying the album."

That may be what's happening with D4L, whose album "Down for Life" has sold 304,000 copies — paltry compared to "Laffy Taffy." But label chief Moscowitz says, "I don't look at the album sales as a disappointment at all." He notes that weekly sales of "Down for Life" increased by roughly 50 percent between the second week of November, when the album was released, and Christmas — a rarity in rap, where sales typically peak in an album's first week of availability.

"To me," he says, "that's a sign that people are converting over and buying into the group. And that singles sales didn't necessarily erode the album sales."