love the laffy taffy...

But snap music's best-known chant is "Shake that Laffy Taffy, shake that Laffy Taffy." That's the refrain from an utterly infectious song called "Laffy Taffy," by D4L. It has been hanging around the upper reaches of the Billboard chart since before Christmas, and last week it officially became the most popular song in America.

There's only one problem: people aren't buying the album. D4L released its debut album, "Down 4 Life" (Dee Money/Asylum/Atlantic), in November; according to Nielsen SoundScan, it has sold about 230,000 copies so far. That's considered a success if you're an alternative-rock group, but not if you're a Southern hip-hop group, and especially not if you're responsible for the biggest song in the country. In fact, it's one of the lowest sales totals for a chart-topping act in years.

In another category, though, D4L is setting sales records. Last week, the group sold 175,000 digital copies of "Laffy Taffy." That figure doesn't just set a digital-download record, it smashes the old one: the previous record-holder was Kanye West, who sold 80,500 digital copies of his hit "Gold Digger" one week last fall. D4L has now sold more than twice as many digital downloads as CD's. The group's members - Fabo, Shawty Lo, Mook B and Stoney - aren't just chart-toppers; they're music industry pioneers, too.