POP WEEKEND : FROM MOSCOW TO L.A. : RAP’S NIGHT OUT AT THE ARENA

There were police and security guards on foot and in patrol cars by the score. They were even positioned on the roof of the Los Angeles Sports Arena. They weren’t there in anticipation of terrorists, but rather for the throngs of teen-agers who turned out Friday for an evening of rap music supplied by L.L. Cool J, Whodini, Public Enemy and Doug E. Fresh & the Get Fresh Crew.

Locally, rap music’s audience is largely composed of the under-21 set, and Friday it appeared to be a fairly even mix of black, Latino and white fans. But, being a style of music born out of the New York gang scene, rap also attracts gang folk here--most resoundingly last year when 40 people were injured in violence at Run-D.M.C.’s Long Beach Arena concert.

Rap’s performers and supporters have tried hard to emphasize that their message is positive and non-violent, and the recent Run-D.M.C./Beastie Boys tour was trouble-free, but rap obviously still makes people nervous.

So one could tolerate being frisked and put on a very intimate basis with hand-held metal detectors upon entering the arena. One could also tolerate the nagging thought that at any moment a stray bullet might whiz past one’s head in the parking lot.

Fair compensation for all that tension would have been an evening of definitive, hard-hitting rap--and that was something in short supply Friday night.

Rap is often based on rat-a-tat-tat verbal assaults laid atop a jackhammer, percussive beat, and in order for it to mean anything at all, it has to be decipherable. But Public Enemy was shackled by a substandard sound system that allowed little of what they said to come through crystal-clear, save for the often repeated F-word--which for some reason is always decipherable.

With two of the six members aiming machine guns (unloaded, we’ll presume) at the audience, the New Yorkers ran through what they referred to as a “terminator mix,” though it was dull rather than dangerous.

“Let’s see the fist of solidarity,” demanded leader Chuck D., and that got some response from the hundreds of kids clustered near the stage. But the audience seemed to be saving its solidarity for Doug E. Fresh--just your basic clean-cut kid in a genre not generally known for that.

Clad in a jogging suit and running shoes--the wardrobe of choice for rap artists and their disciples--Fresh had energy to spare on “All the Way to Heaven,” whose lyrics the crowd knew by heart as they chanted along. But his set was cut short when a fight broke out in the lobby, and as mobs of teen-agers raced from the concert area to watch, Fresh quickly exited the stage.

The two-man Whodini, backed by three hip-grinding male dancers, worked the stage like old pros on raunchy, image-defining hits like “Freaks Come Out at Night” and “I’m a Ho.”

This veteran group is slicker and more performance-conscious than many rap artists, most of whom are still in the deejay-on-the-turntable and the “let’s-just-stand-around-talkin’ ” stage. That anybody-can-do-it simplicity is at the heart of rap’s appeal, but it also limits the music’s potential for a broader base.

Headliner L.L. Cool J has the range, sophistication and showmanship to appeal to the same audience lured to risk-taking artists like Prince. He even resembled Prince on “I Need Love,” an R-rated ballad embellished by his carnal moves on an overstuffed couch.

With his braggadocio style, this 19-year-old has muscled in on territory previously staked out and conquered by Run-D.M.C. and the Beastie Boys: His current album, “Bigger and Deffer,” is No. 1 on the black charts, and--more significantly--made the pop Top 10.