Imagine listening to a whole bunch of the songs that you've heard on the radio, or at parties, or at clubs, or in your room, for the past 10 (or 20, or 30) years, all at once, ricocheting and popping up against each other in a manic sonic emotional mnemonic soup. Whup, there's the booty bounce with that guy in college and, ohhh, that song I listened to when we broke up, and yeah, there's the one that was always on the radio when we went out two years ago.

That's roughly what it's like listening to Girl Talk — real name Gregg Gillis, a 27-year-old former biochemist from Pittsburgh whose dizzyingly dense pop music mash-ups have made him the talk of the music world.

Take Gillis' latest recording, "Feed the Animals," released last year, in which fragments from more than 300 songs from the 1950s to the latest hits jostle into unexpected harmony in 53 minutes.

On one track called "What It's All About," Beyonce's "Ring the Alarm" meets Queen's "We Will Rock You" before the song twists into a melange of DJ Funk, Phil Collins' "In the Air Tonight," the Beastie Boys' "So What'cha Want" and The Police's "Every Little Thing She Does Is Magic" which leads to The Cure and Busta Rhymes — and that's just the first minute.

Above all, Girl Talk is a celebration of the power of pop, even for those who think they're too hip for pop.

"I enjoy listening to the Beatles, ABBA," Gillis says. "I don't want this to come across as ironic. I want to be very sincere about it. I listen to pop, and I am a fan."

Since 2006, when "Night Ripper" brought Girl Talk to the forefront of the alternative music scene, the act has topped "best of" lists at Rolling Stone, Spin, Blender and Pitchfork.com, and played major festivals like Coachella and Bonnaroo. His shows, where a dancing audience floods onstage to surround a sweating Gillis, stripped to his boxers and working his laptop, have become a club circuit phenomenon.

Although Gillis' virtuoso manipulation of songs has earned him media attention, his condensation of what music fans like best has made him so popular, says Jon Pareles, pop music critic for The New York Times. "He takes the hooks, the stuff everybody knows, one blast of the familiar after another," Pareles says. "It's a sugar rush. It's all the easy stuff in one snappy package."

Gillis developed an open mind about music early on. As a third-grader in Pittsburgh he listened to everything from experimental noise music to underground rock and hip-hop on the local college radio station. In high school, he started an act with shows that might consist of 10 boom boxes playing skipping Madonna CDs accompanied by guitar feedback.

"That was my teen rebellion, my punk rock," Gillis says. "I liked Nirvana and loud guitars in third grade, so by the time I got to eighth grade it just didn't seem interesting anymore."

But if Gillis was more inspired by experimental music's free use of accidental or ear-grating sounds than by the gritty guitar-hero thing, he also took guilt-free pleasure in pop and hip-hop. "I was into going to a Spice Girls concert and then playing a noise show the next day at an art gallery," Gillis says. "I was about the extremes of pop and underground, as opposed to Korn and Limp Bizkit."

He started Girl Talk in 2000, during his freshman year studying biochemistry at Case Western University in Cleveland, playing at art galleries and alternative music venues. He thought the name's frivolous connotations would provoke "serious" music audiences just as he hoped his use of popular music would break with avant-garde conventions.

One of his models for Girl Talk was hip-hop, where Jay-Z's lifting of a piece of "Hard Knock Life" from the musical "Annie" or a funky James Brown sample could trigger memories and emotions in a way that abstract sound mixes did not.

"I'd think, 'Wow, that's amazing they're putting a whole new spin on it, a whole new attitude and context,' " Gillis says.

Gillis' first recording, "Secret Diary" in 2002, was a mostly noise-filled avant-garde mix. He began using a more accessible blend of pop music in 2004's "Unstoppable" and the breakthrough in 2006 with "Night Ripper," an album that caught critics' and audiences' ears and took him from playing shows for a couple dozen people to roiling club crowds and the huge festivals.

Meanwhile, the antics like dancing round the room or stripping off his clothes that Gillis had long used to startle art gallery audiences (and keep himself entertained) began provoking a different and hugely enthusiastic response from pop crowds.

The shows have become an integral part of the Girl Talk phenomenon.

"Girl Talk set off instant pandemonium as its set began at Terminal 5," Pareles wrote in The Times last November. "His main physical challenge was getting to his laptop ... amid the crowd of dancing, shouting fans, some of whom were eager to massage him as he worked."