The success of a U.K. music genre known as grime, championed by the likes of Dizzee Rascal, has made rapping to mobile phones a popular pastime for a lot of British young people.
On the street, cell phones enable impromptu rapping, or "spitting," over music played through speaker phones.
If MCs or rappers want to try out their "bars," or rhymes, they can "flow" over beats played over the speaker phone.
Instrumental music is downloaded from sites like Rewind and transferred to the phone via Bluetooth or infrared.
Friends hang out outside, "spitting in groups around the streets," said music producer Joelle Reefer.
"They wave their arm in front of themselves, like they are telling off a small child," Reefer wrote in an e-mail, describing the dance style currently in fashion on the U.K. garage scene. "Shaping and pointing their fingers to resemble guns, (they) start to spit/rap in synchronization one after the other, spitting a 16- or a 32-bar rhyme."
If the inspiration starts to flow and the participants really get into the music, they start to "hype" it up.
"'Hype' or 'hyping it' means over-excitement," wrote Reefer. "This is when a group of guys 'jam' around a phone."
The music can be shared via Bluetooth "very quickly" and for free, Reefer said.
Reefer works at the South London youth project Kickstart Youth Inclusion Project, a role that enables him to witness firsthand what British youth are doing with their phones.
He has seen the craze coinciding with the addition of MP3 players and enhanced speakers in newer phone models.
Cell phones are also indispensable if inspiration should strike when the budding grime lyricist is out and about.
"If I'm not at my house and not got a pad and pen, I go to the note pad (in the phone) or type into a message and save it into the outbox," says Vortex, an 18-year-old MC from East London whose first mix tape will soon be released. "It can be just a punch line or a metaphor."
Fifteen-year-old Sparx, a South London schoolgirl and aspiring MC, agrees.
"If I was on the street and I had no music, I'd write it into my phone," she said. "The phones are so important round about here. (If) I didn't have my phone, I don't think I would do it."
Established artists such as MC Shystie use their cell phones as a mobile office.
According to her manager, Justin Stennett, MC Shystie uses her phone "like a laptop." She writes lyrics using text messaging, and often uses the voice recorder on the phone. When she's finished working in the studio, she takes tracks with her as MP3 files on her phone.
U.K. mobile-phone operators have been falling over themselves to sell music services on mobile phones, sponsoring numerous music festivals and selling services like track downloads, streaming music or videos.
But people in this scene use their phones in ways the industry can't cash in on.
For instance, pirate radio stations were the first broadcasters to embrace text messaging as a way to interact with listeners, long before it became the norm at Britain's commercial radio stations. Pirate stations commonly allowed listeners to request a "rewind," or replay, of popular tunes, and to send messages to the DJ at the station.
But these days, pirate radio MCs tell listeners to rack up "missed calls" if they like a song, by calling the station's cell phone and letting it ring just once.
"It's a good way to see if the listeners like the tune," said Purple, a pirate radio MC. "Text messages sometimes take a long time to get to us. Sometimes a message asking for a rewind will arrive six or seven tracks down the line. A missed call is quickest."
And nobody pays for the call.
While a lot of people in the grime scene may not fall into the target age range for mobile music services, they are not all low spenders. Vortex might spend 50 pounds ($87) a week with U.K. operator 3, but he's not prepared to buy their music videos.
"I'd rather just watch them in my house than pay money to watch them on my phone," he said.
According to Nitesh Patel, senior analyst at industry research firm Strategy Analytics, this reflects the response of a group of young professionals when surveyed about such music services on their phone.
"They thought it was a waste of money and the experience was painful," said Patel.