OC LIVE : At the Harp Inn, Informality Is Strictly Enforced

“Rule No. 1. . . . There are no [expletive] ties allowed at the Harp Inn on a Friday night.”

So pronounces Terry Casey, holding forth from the stage at the Harp where he entertains four nights a week--Fridays and Saturdays when he sings with the Fenians, one of the county’s most popular Irish bands; Sundays when he works solo, and Thursdays when he fronts a trio.

It’s an appropriate warning. Casey’s gigs tend to be boisterous celebrations. They kick off with traditional Celtic music, then progress a few centuries into rock ‘n’ roll--not that the two don’t overlap frequently, as is evidenced by the wild abandon on the small dance floor as either type of music is played.

Great music aside, the Harp--tucked quietly off Newport Boulevard in Costa Mesa--offers a chance to relax with good folks over good pints, which also might explain why it draws such a large, diverse and loyal following.

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A testament to family ownership, it has weathered a recent upsurge in popularity with surprising ease. The only drawback now: There usually is a 15-minute wait to get in on the weekends. But it’s worth it.

There’s no cover, and a 20-ounce glass of Guinness goes for a reasonable $3.50. The best thing about the Harp, though, is the people in it, loosened, perhaps, by the hundreds of pints poured nightly (McEwan’s, Harp, Bass, Newcastle and Carlsburg also are on tap) or by indulgence in the full bar service. New faces are welcomed, first by the jovial doormen who keep the line out front entertained, and then by the regulars crammed three deep round the bar.

Come prepared to discuss the Bruins, the Celtics, the Red Sox or even international club soccer. Gerry Mackey, who owns the place with his wife, Pat, is president of the Gaelic Athletic Assn. of Orange County and knows quite a bit about sports, along with other pressing issues of the day, on which everyone seems to have an opinion, solicited or not.

P.S. Expecting guests from out of town for the holidays? The Harp’s weathered charms probably will be appreciated by East Coast types, who often carry on about the absence of authentic pubs in California (or even west of the Mississippi). In any case, mark down the second Sunday of December, when the Mackeys will be serving turkey, ham and all the trimmings at 4 p.m. to all their customers as a way of thanking them for their support.

* THE HARP INN

* 130 E. 17th Street, Costa Mesa.

* (714) 646-8855.

* 4 p.m. to 1:30 a.m. Mondays through Thursdays; opens at 2 p.m. Fridays and noon Saturdays and Sundays.

* American Express, MasterCard and Visa.