"Smells Like Booty." "A Stroke of Genie-us." "I Just Can't Get Enough Pills." The song titles say it all.

Music's latest craze is certainly a twisted one. Some are even calling it bastard pop. How else do you explain Destiny's Child singing "Bootylicious" over Nirvana's sacred "Smells Like Teen Spirit"?

The new genre-crossing format, however, has an obvious father in Napster, Gnutella and their controversial file-sharing siblings, who have fed the frenzy by making a capella and instrumental tracks available to any wannabe producer with a decent hard drive.

Give an armchair DJ some simple remixing software, like Acid, and within no time you'll be hearing the next "Get Ur Faith On" or "My Name Is Funk Soul Brother."

The art of bootleg remixes, mash-ups or sound clashes (take your pick) emerged as an Internet phenomenon two years ago but is now scratching its way into the commercial music market, especially overseas.

In Europe the pioneers of the movement, such as Kurtis Rush, Soulwax, Osymyso and Freelance Hellraiser, have become household names, headlining popular clubs and spinning their creations on radio shows. One mash-up artist, Richard X, even recently topped the UK singles chart with "Freak Like Me," which layers vocals from the Sugababes and Adina Howard over new-wave hero Gary Numan's "Are Friends Electric."

Bootleg remixes would likely be all over the charts, except they happen to be illegal — unless, of course, the remixers can score permission from the artists they use. And that's not easy, considering they are generally going for the oddest combinations possible. When Dave Grohl heard about "Smells Like Booty," for instance, his response was, "It sounds like a f---ing mess."

Clearing samples is also painfully time consuming. 2 Many DJs (Soulwax's David and Stephen Dewaele), spent more than six months getting permission for the 114 (they wanted 187) tracks used on their debut, As Heard on Radio Soulwax Pt. 2. That's probably why nobody bothered for The Best Bootlegs in the World Ever, an unauthorized compilation that independent record store owners worldwide have had a hard time keeping on their shelves.

Perhaps, though, the biggest sign that mash-ups are going nowhere but up is the support they have garnered from artists who are being "mashed-up."

"We encourage kids out there doing that," Papa Roach singer Jacoby Shaddix said. "Be creative, man. That's what the music's there for. Technology is crazy these days. You could morph a chicken and a hip-hop song. ... I don't know, it'll be something. Mix us and a Lionel Richie song!"

The hip-hop and electronic music communities are especially supportive, recognizing that parts of their genres are based on the same credo of taking something old and making it new. That musical approach can be traced back even further, into the '70s, when Jamaican DJs would mix a capella reggae tracks with dub instrumentals. The term "mash-up" comes from the Jamaican phrase "Mash up the place."

Still, it was hip-hop that made borrowing other recordings artistically acceptable, and the bootleg remix trend is reminding artists of rap's early days.

"Around 1990 in New York, all the hip-hop acts put out 12-inch singles of their songs with a capella versions on the back," recalled former Soul Coughing singer Mike Doughty. "I would go to all these clubs and hear Mary J. Blige's 'Real Love' over a hundred different hip-hop instrumentals. Some of them were just genius. It was a wonderful, free, creative time. Doing it on ProTools rather than a couple of turntables is just a new spin on it."

Jermaine Dupri, a pioneering producer in his own right, is keeping a watchful eye on the mash-up artists.

"We as musicians, we should just catch up to what the kids are doing and just start collaborating and making records," he explained. "They're showing us a sound that obviously they like, and we should possibly try to explore that sound and go see what will happen if you put this person with this person and this person and that person. If they do one of my records, I'm definitely gonna pay attention to it and take heed to it and go call the person that did it and make a record."

Moby, who launched his career remixing singles for Michael Jackson and other pop stars, believes bootleg remixes are another way for more creative minds to get into the game. "Everyone is becoming a musician," he said. "Anyone with a computer has the ability to make good-sounding records, and I think it's really exciting."

Moby is flattered that a few of his songs have been remixed, and he's not alone.

"It's a compliment, like having Weird Al cover one of your songs," said former Faith No More singer Mike Patton, who at last count was in six bands, including Tomahawk and Fantômas.

Electronic music luminary BT, who also produced 'NSYNC's "Pop," was so impressed with a mash-up of his "Mercury and Solace," he tracked down the remixer and released it.

"I love having people do unsolicited remixes of my stuff. In fact, I'm thinking about posting vocals of the whole next album on my Web site when it's done," BT said. "I believe that everyone uses sounds in a case-specific and different manner than other people who use the same sounds."

BT is especially fond of mash-ups that pair drastically different songs. "I'm an avid believer in crossing boundary lines and idiom subdivisions in the music-making process, and if we need to mix Willie Nelson with John Cage to push the envelope in the right direction, then bring it," he said. "That actually might be pretty dope. I may try that."

Julian Casablancas, singer of the Strokes, is a supporter of bootleg remixes, but he was disappointed when he first heard Freelance Hellraiser's "A Stroke of Genie-us," which pairs their "Hard to Explain" with Christina Aguilera's "Genie in a Bottle."

"I think it's a nice try, but I thought her vocals actually fit through the whole song, which would have been a funny coincidence, and I would have probably enjoyed it, but they sort of edited it so the guitar plays five different chords in the verse," Casablancas said. "It's like they just looped the first chord. They could have just done it with anything. It was a little unimpressive. If it had worked, I would have probably promoted it. It was a funny idea, but it seemed like a little bit of a cop-out. The funny thing is, Christina Aguilera's on our label."

Despite Casablancas' opinion, "A Stroke of Genie-us" is one of the most popular mash-ups, even sneaking onto radio shows in America. But whether it or other bootleg remixes — like the dozens using Missy Elliott's "Get Ur Freak On" or Eminem's "My Name Is" — will ever be legitimate Stateside hits remains to be seen.

"I've been played on college radio [in the U.S.], but I think the big radio stations are too genre-based," Freelance Hellraiser said. "Mash-ups by their very nature exist to combine and ultimately destroy musical genres, which makes them difficult to pigeonhole."

Added Patton, "I could see one of these crossing over, but they are usually a little too twisted for the simple mind to get a grip on."

Mix Master Mike, who DJs for the Beastie Boys and makes his own sound collage albums, thinks there is at least one U.S. native who can truly break the genre in America. "DJ Z-Trip mixes Christina Aguilera with AC/DC and stuff like that, and it's creative," Mike said. "And it's funny."

Steve Mannion, co-editor of the popular mash-ups Web site Boom Selection, pointed out that the style is still growing. "It's really down to the technology," he said. "As that develops, so will the methods people can use to be creative. Eventually, technology may be so advanced that making any two songs sound good together is possible."

Hellraiser, who said his DJing bookings and offers for legitimate remix work have increased since the mash-up boom, believes the genre can survive because of the infinite number of crazy mash-ups that have yet to be done. "I'd do a bootleg of the Lord's Prayer if I could find the a cappella," said the DJ, whose favorite mash-up mixed the Doors with Nas.

On the other hand, there are artists in electronic music — a genre where the hot styles changes monthly — who see the popularity of sound clashes fading away.

"It's cynical music by cynical tired people with no ideas," said Scottish techno producer Slam. "In the U.K. charts there was a particularly dreadful one with Supertramp vocals speeded up — as if they needed to be — on a trance track. Awful, yet somehow popular."

New York DJ Liquid Todd has nothing against mash-ups, but he said he would like to see computer-savvy kids write their own songs. "That's when we are going to hear some really amazing sampler-based music," he said.