The Guitar Hero video game, which doesn’t require any actual guitar knowledge — flashing lights tell you where to hit the frets on your guitar that correspond with notes displayed on the screen — has become big in bars across the country.

On Sunday nights at Orleans in Davis Square, Red Sox games are shown on small flat-screen televisions by the bar. The big projection screen by the window is reserved for something else: ax -grinding and shredding.

Sundays are Guitar Hero nights , which means the bar is taken over by gamers who battle one another with guitar-shaped joysticks that are used to play anthems by bands like Guns N’ Roses, Metallica, and Nirvana.

"Sunday nights were our slowest nights , so it’s been a big help getting people in the door," said Mike Cotter , an Orleans manager. "I didn’t realize how popular it was."

The video game, which doesn’t require any actual guitar knowledge — flashing lights tell you where to hit the frets on your guitar that correspond with notes displayed on the screen — has become big not only at Orleans but at bars across the country. There are Guitar Hero nights in clubs from New York to Los Angeles. There has been one at River Gods in Cambridge for about a year.

Greg LoPiccolo, who helped design Guitar Hero (versions I and II), said his Cambridge-based company, Harmonix , revels in the fact that the computer game designed for living rooms has become a bar favorite like Keno or darts. "It wasn’t a part of the original vision," he said. "After it happened, it sort of made sense to us."

When Harmonix first heard of a charity Guitar Hero competition held at a Brooklyn bar called Barcade , it sent an employee to check it out. "She was shocked at the level of performance," LoPiccolo said. "People came from all over the five boroughs. We were expecting a drunken, you know, thing. But these people came to play. We found it very gratifying."

Harmonix has kept the bar vibe in mind as it designs its new game, Rock Band, which will be out this Christ mas. While Guitar Hero is built for one to two players, Rock Band will allow multiple gamers to work as a band. "At this point, now that we see what a social experience it is, it gave us renewed confidence in a full band game," LoPiccolo said.

At Orleans, the Guitar Hero night has drawn up to 40 people a week since it started last month. Under bar rules, the night’s top-scorer not only wins the respect of the room but also has permission to play Lynyrd Skynyrd’s "Freebird," which is off limits otherwise. This rule is practiced at River Gods, too.

"It’s like 11 minutes long," said Jeff MacIsaac , who runs the night at River Gods.

Orleans is in the thick of a Guitar Hero tournament in which contestants battle over six weeks for a Gibson Signature electric guitar. The third installment of the competition is tomorrow night at 10. Anyone who is over 21 can join in, and there’s no cover.

In New York, a new Guitar Hero night has quickly become a hit at Pianos on the Lower East Side. Jasper Coolidge of Pianos said the bar stole the idea from Barcade after seeing how many people showed up for its Guitar Hero event. He likens the bar appeal of the game to karaoke. "But with karaoke people need to get drunk," he said. "Guitar playing is such a showy flashy thing. Add some alcohol, add members of the opposite sex, or the same sex, and it becomes like going to a party in your parents’ basement."

Since the Pianos night started last month, it has been featured in the Village Voice and Time Out New York. The night has drawn staffers from "The Daily Show" and "The Colbert Report," who work nearby.

"They’re big Guitar Hero fans," Coolidge said.

Pianos is also in the early stages of planning what Coolidge calls a "real geeky virtual tour" so that Guitar Hero champs from New York, Los Angeles, and other major cities can face off for a national title.

Coolidge is anxious to pit New York against Boston, not surprisingly. "Kind of like baseball."

Even if the New York shredders fail to show, Cambridge and Somerville could have their own battle. MacIsaac, who hosts the River Gods Guitar Hero night the last Tuesday of every month (including May 29 at 9), says his regulars, who have historically played for fun, have started requesting a more organized competition so they know who’s best.

"We definitely have some characters who are crazy good," Mac- Isaac said, mentioning one regular who brings his own wireless controller in a special case. "He’s like a nerd equivalent of Paul Newman [in ‘The Hustler’]. He brings his own cue stick in a box."

Via the Boston Globe