If you've been to recent shows by Green Day, Clay Aiken, the Backstreet Boys or Avril Lavigne, then you know that a lot of the serious action isn't going on in the front row or the pit. It's on the big screen next to the stage, as messages like "Nirvana Rulez!" and "We Luv A.J.!" scroll across LED displays.

As if there weren't already enough going on at a live concert, many fans can now spend the downtime between bands texting photos and messages to their friends in the venue via the big screen. In some instances, they can leave those homemade signs in the car, because the bands might even answer queries from the stage.

"We've done this at bars with 30 people and at shows with 40,000 people, and the dynamics are totally different," said Alex Campbell, CEO of Chicago's Vibes Media, one of a growing number of companies that supply venues with the software to do in-house text messaging. "At a House of Blues show with 2,000 people, it's more of a back-and-forth conversation and interaction between people, like at a Las Vegas [show] with Hoobastank where we had a guy dump his girlfriend via texting and then all these other guys were trying to pick her up. But at a show with 30,000 people, it's just about getting your name up there and giving a shout-out and getting noticed."

The first big tour to employ Vibes' software was Green Day's American Idiot outing, which started last year. The company has also deployed it at recent gigs by Simple Plan and the Black Eyed Peas and will be rolling it out for Gwen Stefani's solo tour. The software can be changed depending on the show: There can be a static screen that is available to texting from the minute the doors open until the first act plays, and then again in the break before the main act; or, in the case of the Backstreet Boys' recent tour, a CNN-like scroll at the bottom of the screens between sets.

"We really enjoyed having it because it was a good way for fans to be interactive at the concerts and another way for fans to interact from home with the shows," said Backstreet co-manager Kenneth Crear. "Fans from the next city could send in messages saying how excited they were for the show the next night and the guys could react to and answer some of the messages during Web chats after the shows from their tour bus."

Crear said the Boys, using a computer backstage, would scroll through messages that ranged from "We love you" to "A.J., will you marry me?" to "Brian, how are your kids?" With up to 2,000 messages coming in per show, the volume was heavy, but as long as fans are into it, Crear said the band will continue to feature texting during its shows.

"Who knows? Someday in the future we might take a segment of the show and stop what's going on and have them respond onstage," he said.

Vibes' original version of the software was developed in 2002 for a show by DJ Paul Van Dyk in Chicago, when the visual producers were looking for something for people to do during Van Dyk's set to stimulate them. Unlike those renegade days when whatever you sent went right up on the screen, now the companies that coordinate the texting either use live "text DJs" or artificial intelligence filters that rank messages based on their appropriateness and the parameters set by the venue. Messages -- for which standard, and in some cases premium, rates apply -- will typically show up within five seconds. Several thousand can make it up to the screen every hour.

Sprint, one of many major carriers that offer the service, coordinated the texting at a recent Avril Lavigne show and has signed on to provide the service for Bon Jovi's upcoming tour in support of their new album, Have a Nice Day. "It's not a moneymaker for us, but we're hoping that as it becomes more popular it will become a standard part of what the tour manager thinks about when he's putting together the lighting, pyro and other equipment he needs for a tour," said John Styers, director of data communications services for Sprint.

"This really extends what is typically a two-hour event into a longer experience," he continued. "An hour after the show you can ping the phones of the people who sent messages and let them know about a special Web site with exclusive behind-the-scenes material and more information on the band."

Bands are using texting for a wide variety of purposes during their shows. Coldplay encouraged fans to text their e-mail addresses to the anti-poverty campaign by Oxfam using technology similar to that used on U2's world tour and during the Live 8 shows in Philadelphia and Edinburgh, Scotland.

The Rolling Stones have yet another unique texting application on their A Bigger Bang tour. Fans attending certain shows on the tour can text a message as soon as they arrive at the venue and, through a random drawing, win a chance to sit onstage during the show.