One thing became clear by the time the WAMO Summer Jam Saturday at the Mellon Arena had finished. Musicians who sing and enunciate their lyrics perform better than those who scream the words.

The screaming delivery is often heard at a rap concert. The artist will try to excite the crowd by being more intense on stage. Better to take a lesson from, say, Talib Kweli and Saul Williams. They allow the audience to appreciate what they say -- by letting the words do the work.

At the WAMO jam, the singing group Pretty Ricky -- Tavion La'Corey Mathis, Diamond Blue Smith, Spectacular Blue Smith and Marcus Ramone Cooper -- brought along a good stable of songs and delivered them well. The audience appreciated it and helped sing some of the lyrics.

Lil Scrappy came on next. He was a screamer, and was overly profane. He would ask the women in the audience whether they had a clean bill of sexual health, and dropped the n-word so often that you came to the conclusion that Al Sharpton is losing the war against the racial epithet. The highlight of his performance came with "Money In The Bank." At least he was honest about what motivated him to become a rapper.

"You know what I'm sayin'?" he asked the crowd.

Not really. Perhaps he should have relaxed a little bit more for his set. But he did well on an a capella ending to "Livin' in the Projects."

Wiz Khalifa, the current darling of Pittsburgh who just signed to a major record label, was next. He is more of a storytelling rapper than a catch-phrasey one. His lyrics shined through on "Pittsburgh Sound" and "Damn Thing." On other songs though, the loud background beats often overshadowed his voice -- and the stories he had written.

CRAVE, another local act, came on next. They were presented with the key to the city by a representative of Mayor Ravenstahl. Women seemed to be especially fond of the group. Their soulful voices were reminiscent of The Temptations, even if their bumping and grinding was not. .

The group asked for a moment of silence for the Larimer children who died in last month's fire.

Young Jeezy came on with bundles of energy. He wasn't screaming, though. He had a high intensity and a crisp delivery. His best songs were shortened versions of "Sole Survivor" and "Go Getta," which was his last song on stage.

Mario was next. The highlights of his set were "How Do I Breathe" and his 2004 hit "Let Me Love You." He reminded me of Usher.

After Mario left, DJ Unk performed "Walk it Out" and "2 Step." Five women went on stage and danced, while many other women in the audience walked it out and two-stepped it.

The last performer was Lil' Wayne, who took the stage 30 minutes after DJ Unk left. His performance was worth the wait. The rapper's delivery was laid back -- less aggressive than Young Jeezy, but just as good. His best songs were "Back that Azz Up," and "Money on My Mind."