Rap spins off a new style every six months or so, and sometimes it's hard for older rappers to keep up. L.L. Cool J, who's still in his early 20s, counts as an older rapper; he's been making hard-hitting party albums since 1985. His 1989 record, Walking With a Panther, contained an uplifting message, but only in the liner notes. ''I am young, black and legal,'' he wrote. ''I want to do my part in breaking stereotypes placed on young black men in America.'' But now he's older, and rap has grown more political. His convictions make their way into his music; the last cut on his new album, Mama Said Knock You Out, is a song about morals and religion called ''The Power of God.''
There are other new developments, too. A second track, ''Farmers Blvd. (Our Anthem),'' also breaks the party mood, this time to take L.L. Cool J back to the rough street where he grew up. Another, ''Mr. Goodbar,'' portrays a man on the prowl for women as a nervous predator; still another, ''Cheesey Rat Blues,'' is a picture of a lowlife rapper who never quite made it. L.L. Cool J who's about to make his acting debut in The Hard Way, a movie starring Michael J. Fox and James Woods has widened his range and darkened his outlook. This album is stronger and more consistently memorable than any he's made in the past.
And yet there's something inconsistent going on. God will punish drug dealers, we learn. But we also hear (in ''The Boomin' System,'' the first single) how nice it is to have a monumental sound system making tidal waves of sound in your car, and that L.L. Cool J is the best rapper alive. The several songs that make that last point are easy to ignore, because they have no character. (There are fewer of them than there were on the last album, another sign that L.L. Cool J is growing up.) But it's not easy to reconcile serious religion with booming loudspeakers, or with brand-name luxuries cited in songs like ''Mr. Goodbar'' and ''Around the Way Girl,'' where the women we hear about always seem to be carrying Fendi bags.
L.L. Cool J did say in the liner note to his last album that in defiance of stereotypes he wanted to prove a young black man could reach ''all materialistic goals'' strictly by lawful means. That might explain why he keeps talking about alligator shoes. But he's made that point by now. Isn't it time to forget those Fendi bags and get on with the serious business of life? B