L.L. COOL J ATTEMPTS TO SCALE THE POP MOUNTAIN

Though rap music--spunky, rhythmic chatter recited to a funky beat--has powered its way to the fringes of the pop mainstream, it’s not likely to get any farther until it produces a genuine star.

The Fat Boys, Run-D.M.C., Kurtis Blow and Grandmaster Flash are successful, but primarily in the cultish world of rap. They haven’t captured the hearts of the pop masses. Many observers are predicting that L.L. Cool J, the hot new solo rapper whose real name is James Todd Smith, will be the one to plunge rap music into the mainstream.

L.L. Cool J, an abbreviation for Ladies Love Cool J, is a torrid rapper, spewing out street talk at a jaunty pace. According to admiring critics, who have dubbed him rap’s “intellectual,” his lyrics are more far-ranging and insightful than the usual rap chatter.

Smith’s first album, “Radio”--on Def Jam, distributed by Columbia Records--is on its way to becoming a hit. Thanks to the zesty single, “I Can’t Live Without My Radio,” the album has already climbed to No. 50 on Billboard magazine’s national sales chart.

Pop stardom, he admitted, does interest him, but not on just any terms. Only on his terms.

“Some rappers who are trying to be commercial soften their sound,” he explained disdainfully. “They soften the lyrics or the music, maybe both. I’m not going to do that. I’m making my lyrics harder and my music harder. I’ll get into the pop mainstream and I won’t have to change to do it either.”

Smith’s commercial success is surprising considering that his sound isn’t really commercial. What distinguishes him from other rappers is that he doesn’t use music. Drums are his sole support.

“I’m a minimalist,” he insisted. “I break things down as much as I can. I keep it simple and powerful, just my rapping and the drums. That’s all I need.”

But pop radio, which seldom plays his records, needs more.

“I don’t worry about pop radio,” he said. “I’ve captured the teen-agers, like Frank Sinatra did in the ‘40s and Elvis did in the ‘50s. Pop radio will come around.”

Though only 18, he has the poise of a show-biz veteran. “I’ve always been this way,” Smith boasted. “I was never really a kid. I’ve always acted older. That’s because I’ve always hung out with older people. Even now a lot of the people I hang around with are around 30.

“I don’t mind being young. I can deal with people my age too. But I’m not a little kid. I don’t act like one and I don’t want to be treated like one.”

Smith, who was “hanging out” at Columbia Records’ Century City offices, was cocky and haughty, and quite proud of his attitude.

“I’m not meek and I’m not weak,” he said. “Why should I act that way?”

For half his life, Smith has been a serious rapper. At nine, he was the first kid in his Queens, New York, neighborhood to try this steamy street music. Back then he was basically doing what he does now--rapping to a drum beat.

“I used to go to parties and rap,” he said. “I used to rap over other people’s instrumentals. I was crazy about rapping. It was in my blood, in my soul, even when I was a kid. I was born to rap.”

By 13, he was earnestly writing rap lyrics and in search of a record deal. “All I got was rejections,” he recalled. “I just kept at it. I got better with age. I improved my lyrics. When I look back on what I used to write, some of it was a little silly and child-like and unprofessional.”

He might still be in search of a record if he hadn’t met Rick Rubin, the rap mogul who became his producer and helped him refine his lyrics. In late 1984, Smith put out a single, “I Need a Beat,” the first on Rubin’s Def Jam label, which was followed by another single, the romantic rap ballad “I Want You,” six months later.

Those singles established him in the rap community but his screen debut in the rap musical, “Krush Groove,” exposed him to the pop masses. His single, “I Can’t Live Without My Radio” is the best song on the movie’s sound track. He also steals Goldie Hawn’s new movie, “Wildcats,” with a red-hot rap.

Smith is eager to do more movies: “It’s a great way for the world to be exposed to my sound. I could see myself being a star in movies. The world should know about me.”

LIVE ACTION: Neil Young, Kris Kristofferson and Kevin Cronin of REO Speedwagon have been added to the lineup of Monday’s Forum concert saluting Vietnam veterans. Other stars in the show are Herbie Hancock, Graham Nash and Charlie Daniels. . . . Amy Grant, with opening act Steve Taylor, is scheduled for May 2 at the Forum. . . . Saxon and Armored Saint will perform at the Santa Monica Civic Auditorium on March 29. Tickets on sale Monday. . . . Emmanuel will star in an April 12 show at the Universal Amphitheatre. Tickets go on sale Sunday. . . . Hiroshima will appear March 21 at the Beverly Theatre. Tickets are available Monday. . . . Johnny Thunders, the former New York Doll, will play at Fender’s in Long Beach on March 21.