Bootleg Battle Lines

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By Larry Hardesty

He's also more skilled than many at acquiring raw material in the first place. The digital files from which mashups are made are rarely complete recordings; they're usually isolated vocal or instrumental tracks. Recently, it's become more common for recording artists themselves to release disaggregated tracks to encourage mashup artists to remix them. Sometimes record labels will leak the tracks unofficially, to drum up publicity. Sometimes engineers spirit raw tracks out of the studio: once they're posted online, they rapidly propagate through the mashup community. Disaggregated tracks can also be found in surround-sound recordings and video game software. But if no such option is available, mashup artists have to try to extract the material they need from complete recordings.

Roseman wrote a book, Audio Mashup Construction Kit, that has a 40-page chapter called "Unmixing," about isolating vocals and instrumentals. One of the tricks he describes is to find a section of a song where an accompaniment figure repeats for a few bars before a vocal comes in. Software can then, effectively, subtract the repeated figure from the final mix, isolating the vocal line.

It's Roseman's artistic instincts, however, that set him apart. Like Girl Talk's mashups, Roseman's generally sample multiple songs: his biggest hit, "United State of Pop," borrows elements from all of Billboard's top 25 songs from 2007. But rather than string his samples together in long chains, as ­Gillis does, Roseman gradually layers them over each other, adding texture and building momentum as a song progresses.

A good example is the hypnotic "Stairway to Bootleg Heaven," which borrows tracks from seven different recordings. The heart of the mashup is the juxtaposition of an '80s Eurythymics song and a cover of Led Zeppelin's "Stairway to Heaven" by, of all people, Dolly Parton. On its own, the unlikely and surprisingly effective pairing of synthesized rhythm section with fiddle and mandolin would be enough for a memorable mashup. But Roseman goes further, adding a minute-and-a-half introduction that combines a piece by performance artist Laurie Anderson with a song by the synth-pop band Art of Noise. Toward the end of the mashup, a sample from the Beastie Boys' "So What'cha Want" adds urgency, and at the song's climax, Pat Benatar's "Love Is a Battlefield" enters in double time. Throughout the mashup, as a kind of connective tissue, a sample from the Beatles' "Because" floats in and out, spectral and mysterious. Although several of the recordings Roseman samples sound dated if not risible on their own, the combination is sublime.

Roseman hasn't enjoyed nearly the popular success that Gillis has (though his work is by no means obscure: "United State of Pop" was one of the 100 most-played songs on pop radio for several months in 2008, and his remarkable mashup of Kanye West's "Love Lockdown" and Radiohead's "Reckoner" met the approval of West himself, who posted the accompanying video on his website). Still, if the question is whose mashups we'll be listening to 20 years from now, I know who I'd put my money on.

Larry Hardesty is a Technology Review senior editor.