A little bit of this, a little bit of that

At first, it sounds like a radio broadcast caught between two stations.

Paul McCartney pounds out the opening Fats Domino-influenced piano riff of ''Lady Madonna," but the voice you hear first isn't his. The Beastie Boys cascade across the music's familiar refrain with their nonsensical rhymes from ''So What'cha Want" -- ''Just plug me in like I was Eddie Harris, you're eating crazy cheese like you'd think I'm from Paris." What first is jarring quickly becomes infectious and memorable, an unusual juxtaposition of two classic artists representing different eras and genres.

Cleverly titled ''Whatcha Want, Lady?" the song, by Somerville DJ Bob Cronin, is a ''mash-up," created when existing recordings are digitally blended. The result shows the songs in a completely different context, Cronin says, and creates something ''that's more than the sum of its parts."

Popular in Europe for years, the practice began garnering attention in the United States last year. Now, Cronin (who goes by the moniker dj BC) and fellow self-styled ''mash-up artist" Luke Enlow have started presenting nights in the Boston area called ''Mash Ave." that are entirely devoted to these mixes. Buoyed by the success of their first such night last November, the two will host one tonight and the last Tuesday of each month at River Gods in Cambridge, playing their own creations as well as mash-ups by other producers. They've also begun hosting a ''Mash Ave." night every Friday at Toast in Somerville.

''We started getting into mash-ups maybe like a year ago," Enlow, known in the mash-up community as ''Lenlow," says by phone. ''We came across a discussion forum called 'Get Your Bootleg On' that was basically a place for DJs and producers all over the world to get together and share their stuff. We became part of that community, and we heard about all these great mash-up nights that were happening in England, and that got us thinking about doing something here."

''I was given some [digital mixing] software about a year ago , and I didn't really know what I was doing," he adds. ''For fun I would take parts of songs, mix them together, and make new songs. I shared what I was making with some people on the Internet, and it was well-received."

In November, their first all-mash-up night at River Gods attracted more than 200 people over the course of their four-hour show -- and this was on a Monday night, Enlow quickly adds, when the Patriots were playing. That event featured such creations as Enlow's ''Last Night," featuring three songs with that title by the Traveling Wilburys, the Strokes, and Kid 'N Play, and Cronin's ''Nothing in Its Right Place," a blend of the Roots' ''Don't Say Nuthin' " and Radiohead's ''Everything in Its Right Place," both of which the DJs cite among their favorite remixes.

Also featured were selections from Cronin's project ''The Beastles" -- the Beatles and Beastie Boys -- an idea inspired in part by ''The Grey Album," DJ Danger Mouse's mix of songs from the Beatles' 1968 ''White Album" and rapper Jay-Z's ''The Black Album."

Although ''The Grey Album" was never intended for commercial release, its tracks -- such as Jay-Z's ''99 Problems" married to the Beatles' ''Helter Skelter" -- wound up all over the Internet last year. EMI, which controls the Beatles catalog, quickly issued a cease-and-desist order against the producer. Still, it created an enormous buzz and introduced many to the concept of mash-ups.

(On his website, Cronin has a disclaimer maintaining, ''These mash-ups were created for fun, and as a demonstration of my remixing abilities. The copyright to these source recordings is retained by the original copyright holder." They are not commercially available.)

''I loved 'The Grey Album,' although a lot of bootleggers online kind of dissed it," Cronin says. ''I don't know if they're just hatin' or if they're jealous of Danger Mouse, but I thought it was a great idea. I've always loved the Beatles, and he did a fantastic job."

Even more influential, if less beloved by underground producers, was ''Collision Course," a mash-up of sorts featuring Jay-Z and rockers Linkin Park. Recorded live during an ''MTV Ultimate Mash-Ups" special, the CD, released in late November, sold more than 368,000 copies in its first week and debuted at No. 1 on the Billboard 200 album chart. MTV recently announced there will be five more ''Ultimate Mash-Ups" this year with high profile, but as-yet unnamed, artists.

''The enthusiasm and talent of Jay-Z and Linkin Park really came through on the screen and in the music throughout the 'Mash-Ups' project," Tom Calderone, MTV and MTV2's executive vice president of music and talent programming said in a statement. ''Our goal for 'Mash-Ups' in 2005 is to give more of the biggest artists in the business the freedom to create something entirely new for their fans."

But some mash-up producers don't necessarily view MTV's interest as a boon for their underground art. ''One of the reasons mash-ups are interesting and fun is because a lot of popular music is so terrible right now," Cronin says. ''Major media producers like MTV see someone has done a Jay-Z mash-up online, and say, 'Well, we'll just jump on the bandwagon and release something.' That CD isn't something I'm interested in."

Cronin prefers mash-ups by independent producers such as San Francisco DJ Party Ben. Last month, WFNX-FM (101.7) added his remix of Green Day's ''Boulevard of Broken Dreams" and Oasis' ''Wonderwall" to its rotation, and it quickly became the alternative station's most requested song.

''When we first started playing it, the phones went crazy," says Keith Dakin, the station's assistant programming director, who also hosts a weekday show from 3 to 7 p.m. ''The response was immediate, and I think people like these things because they're funny and cool. It shows the power of Pro Tools [a popular digital production program] and home editing equipment. People have all this editing equipment and can make their own remixes in their basements."

Neither Enlow nor Cronin view mash-ups as a fad, but as yet another innovative means for deconstructing and reinventing existing music. Since most producers are making mash-ups for fun, not profit, Cronin believes this may limit any legal ramifications. Yet, even cease-and-desist orders are unlikely to curtail the burgeoning popularity of mash-ups among DJs, producers, or audiences, the DJs maintain.

''The mash-up scene is subversive by its very nature," Cronin says, ''so I think people will keep doing it."