The console above offers a way to simulate the creation of a music mashup. Six vocal lines and six instrumental tracks have been extracted from their original contexts. Their pitch and tempo have been shifted so that, for the most part, they can be seamlessly recombined. (There are a couple of exceptions, reminders of how difficult matching musical tracks can be.) Click a dial to add or subtract a given track from the mashup mix.

Interactive by Conrad Warre and Alastair Halliday.

Vocals
ABC: How to be a Millionaire (Fry, White) Dazz Band: Let it Whip (Andrews, J.R./Leon "Ndugu" Chancler) Diana Ross: Love Child (Deke Richards/Pam Sawyer/R. Dean Taylor/Frank Wilson) Fergie: Glamorous (Bridges, Christopher/Stacy Ferguson/Jamal Jones/Elvis Williams) Katy Perry: I Kissed a Girl (Cathy Dennis/Lukasz "Doctor Luke" Gottwald/Max Martin/Katy Perry) Robin Thicke: Magic (Gass, J./Max/Robin Thicke)

Instrumentals
Daft Punk: Around the World (Thomas Bangalter/Guy-Manuel de Homem-Christo) Exposé: Point of No Return (Lewis A. Martineé) Falco: Der Komissar (Falco/Robert Ponger) Rick James: Superfreak (Rick James/Alonzo Miller) Bees Deluxe: Roll Over Stockhausen (Warre) Sister Sledge: We are Family (Bernard Edwards/Nile Rodgers)

But among Gillis's fellow mashup artists, the response has been tepid. "The stuff he's putting over the top of a track seems to be like, 'Oh, remember this tune, remember this tune, remember this tune,'" says Tim Baker, who hosts a music-themed podcast called Radio Clash. "It's like you're trying to watch TV, and someone is sitting there switching the channel every 30 seconds."

"Form requires repetition," says Jordan Roseman, who makes mashups under the sobriquet DJ Earworm. "You listen to any pop song on the radio: the elements repeat themselves. They go away, you miss them, they come back, and you welcome them. And just when you're getting sick of them, it goes somewhere else. And just when you start to miss them again, they come back." Girl Talk, however, simply discards each of his samples after it's played for 30 or 40 seconds.

He also tends to pair instrumental tracks with hip-hop vocals, as the analysis of "Play Your Part (Pt. 1)" might suggest. "In the mashup community," says Luke Enlow, a mashup artist from New Hampshire who releases music under the name Lenlow, "that's kind of seen as a cop-out because it's very easy to do, because you don't have to worry about keys matching."

Gillis doesn't deny that hip-hop mashups are easier to do; he just considers that irrelevant. "What the Ramones play isn't very difficult to play," he says, referring to the New York band widely credited with launching the punk-rock movement. "I think of playing the computer as a very punk exercise." He also invokes the figure of Joe Satriani, a rock guitarist renowned for his blisteringly fast solos. "Joe Satriani is not necessarily more important than [Nirvana's] Kurt Cobain just because he can wail on the guitar better," Gillis says.

It's a common pattern in music history, however, that at the moment of a popular form's ascendancy, its most ambitious practitioners begin to move in a more esoteric direction. The sidemen who played in Benny Goodman's small ensembles at the height of swing are one example; the Beatles and Beach Boys in the mid-1960s are another. Mashups haven't yet achieved the type of cultural prominence that jazz and rock did in their heyday, but if there's a similar transitional figure in the current mashup scene, it could well be Roseman.

Roseman double-majored in music and computer science at the University of Illinois, and because he can analyze the harmonies in his raw materials, he can see key clashes looming a mile away. He doesn't have to rely as heavily as his peers do on trial and error to find samples that fit together musically.