What up L.A.? Rap, old-school hip-hop

“You idiot,” 50 Cent said, scolding his DJ for cueing up the Queens rapper’s “What Up Gangsta.”

“The chief of police told me he was gonna lock me up for inciting a riot if I perform this song,” 50 Cent continued, surveying Saturday’s crowd at the Forum as if looking for support. With the near-capacity crowd cheering him on, the chart-topping rapper launched into the confrontational cut, much to the delight of his followers.

50 Cent’s rousing rendition of the incendiary tune capped off a sizzling 50-minute set at 100.3 the Beat’s Summer Jam 2K4. Joined by all but one of his immensely popular G-Unit crew -- Lloyd Banks, Young Buck and the Game (member Tony Yayo did not appear) -- 50 Cent showed he could control the crowd as easily as churn out hits, blasting through such G-Unit songs as “Stunt 101,” “Poppin’ Them Thangs,” “Wanna Get to Know You” and 50 Cent’s smash “In Da Club” as the fans happily danced and rapped along.

With the backing of West Coast hip-hop production architect Dr. Dre and the inclusion of Compton’s the Game in its ranks, the tough-talking G-Unit obviously had an affinity for old-school Los Angeles hip-hop.

However, about half the Summer Jam fans didn’t.

When the Beat on-air personality the Poetess came onstage to announce the impending performance of the West Coast All-Stars, many of the fans -- the majority clearly under 30 -- started streaming for the exits. Those who waited got a rare treat as such Southern California hip-hop pioneers as the Egyptian Lover, King Tee, Rodney O & Joe Cooley, Yo-Yo and DJ Quik delivered sharp mini-sets that highlighted some of their biggest songs and gave an abbreviated blueprint of Los Angeles hip-hop, one of the most dominant and significant brands of rap, thanks in large part to the way it popularized gangster rap through the revolutionary, street-smart work of Ice-T, N.W.A and others.

Saturday’s audience delighted in the charged performances from the rest of the bill, which included some of the most popular rap talent from around the country.

St. Louis’ Chingy tore through a tight 25-minute set just before the All-Stars hit the stage. With a smile as blinding as his shiny jewelry, the party rapper offered playful renditions of his hits “Holidae In” and “Right Thurr.” He also shared the stage with Los Angeles R&B; singer Houston, on whose bouncy hit “I Like That” he also appears.

New York’s Mase made a triumphant return after a five-year retirement, while Atlanta’s Ying Yang Twins and Houston’s Lil’ Flip also delivered commanding performances near the start of the five-hour show.