The vocal trio SheDaisy [ tickets ] may end up being country music's best-selling group by year's end -- and the reason for the Utah-bred sisters' success is as much successful marketing as musical mettle.

Propelled by the success of the single ''Little Good-byes,'' the group's debut album The Whole Shebang on Lyric Street Records jumped up eight spots to #91 on Billboard's Top 200 Album Chart last week and held its ground at #7 on Billboard's Top Country Album Chart, even as Alison Krauss's Forget About It popped in above them.

What explains the rise of these three-part, layered harmonists -- who sound like ''Wilson Phillips with some dirt added in,'' says Lyric Street Director of Product Development Greg McCarn -- is certainly their appeal to urban females in the teenage to age 34 bracket. But record company execs have also noticed a strong contingent of college-aged men at recent radio promotion shows, some of which have attracted 20,000 - 50,000 people.

Lyric Street's promotion of their breakthrough act has depended on some conventional country music marketing, where radio success is critical. Rather than have the group tour with only one big single behind them, Carson Schreiber, Lyric Street's Senior Vice President of Promotion and Product Development, kept the band on a weekend schedule of ''listener appreciation'' radio shows, leaving them free to give interviews, make appearances and sign autographs during the week.

But that alone doesn't explain the sale of 360,000 units since May 11, when The Whole Shebang debuted and immediately went to #1 on Billboard's Heatseekers Chart.

Instead of sending the group to radio station break-rooms and expensive retail industry dinners, the label utilized the connections of its parent company Walt Disney to get director David Hogen (Aliens III, Batman Forever) to make an 11-minute, 35 mm music documentary about the group. Disney also helped book theaters, where radio personnel and key retail buyers got a breezy, quasi-intimate introduction to the band in a novel environment.

''No one had ever done this before... It made much more of an impact than a major dinner,'' says Schreiber.

This synergistic approach also tapped into the Internet, which Lyric Street execs believe spread the band's name through word-of-mouth. Schreiber and McCarns, both RCA veterans, had never launched a Web site for an act this early in its career before, but they're now convinced of the medium's power in the youth market. Users can watch a streaming version of the SheDaisy documentary on the band's site (http://hollywoodrec.go.com/LyricStreet/Artists/shedaisy/index.html), and the label plans to release the group's single ''Before Me and You'' as a download in the broadcast section of the Go Network (http://www.go.com) in the next two weeks.

The label hopes that those efforts, along with continued radio appearances from now into November, will help drive album sales to 750,000 copies by the end of the year. In the meantime, country music fans can expect radio stations to mine more singles from the album.