CAIRO: "We tell the stories of our people, words that come up from our alleys, listen to me to understand" — from the Mahraganat song, "El-Rab El-Masri" (Egyptian Rap) by Sadat, Fifty and Haha.

A new musical sound emerged from the underground in Egypt since the country's 2011 revolution, a rapid-fire electronic beat, mixed with hypnotic rhythms drawn from religious festivals and fired up with auto-tuned vocals. Besides getting club crowds dancing all night long, it has given a rebellious voice to long marginalized youth, telling stories of everyday life in beaten-down neighborhoods of Cairo.

Singers of "Mahraganat" music, from an Arabic word for "festivals," push the limits with their lyrics, riffing on the world of an impoverished young man: sex, girls, drugs, empty pockets, and few options — all in an Egyptian Arabic street slang that leaves many adults in the country's conservative Muslim society befuddled and disapproving.

"We have our own language that no one understands except for us," says Sadat.

Sadat and his friends Fifty and Haha are among the biggest name stars of Mahraganat — their DJ names, of course, which they prefer to go by. The three, all in their early 20s, are childhood friends, neighbors in Madinet el-Salam, one of the sprawling slums around Cairo. They started creating music at home, using an old computer with limited free programs they found online.

Mahraganat evolved from an earlier generation of youth music, known as "Shaabi," roughly translated as "popular," which originated in the 1970s, when working class musicians started producing their own sound.

Shaabi singers were in part inspired by "moulids," or Islamic festivals that feature rhythmic music and mystical poetry, which they turned into raspy voiced songs about the common people infused by Egyptian humor.

Mahraganat, sometimes called "Electro-Shaabi," has amped that sound up to addictive levels, with complex, fast-and-furious rhythms, rhymes and word-play, repeated hypnotically over and over.

It has tapped into a youth public that feels partially liberated — but not liberated enough — by the revolution that toppled autocrat Hosni Mubarak in 2011. The sound became popular in largely underground clubs, with clips passed eagerly among fans on the Internet. With its atmosphere of drugs and sex it's still considered fringe. But it has made moves into the mainstream: It can be heard blaring from party boats on the Nile River and some Mahraganat singers now perform at weddings.

Many of the Mahraganat singers are opposed to Islamist President Mohammed Morsi and the Muslim Brotherhood. Hard-line conservatives see music as sinful — and even the less conservative are scandalized by Mahraganat's lyrics. Still, only a few songs are explicitly political.

"They closed the doors, they raised the walls ... while the people are broken and the destruction goes on and on," the three sing in "Dustour, ya Dustour," about the new constitution pushed through by Islamists last year.

"I love writing about politics and social issues, it's what moves me. But this is not what most people like," Sadat said. "Most want to have fun, so our most popular songs are humorous."

Here's a gallery of photos from the underground music scene in post-revolutionary Egypt.