R&B's old school joined the new on Wednesday (Aug. 13) at the Midsummer Night's Dream R&B Rooftop Concert presented by Caroline Records.

Power actor Rotimi kicked off the evening's festivities by showcasing his singing talents with his new song "Lotto." The 27-year-old singer, who was geeked to be performing on a rooftop for the first time, welcomed surprise guest 50 Cent onstage to join him for their collabo, which helped solidify his deal with G-Unit Records.

"That's my brother," Rotimi told The Boombox. "Being around somebody who's that influential in my life. Also able to rock out with me and believe in me to get on my record is a blessing. And every camera phone came out. It was like 'Whoa.'"

Afterwards, Vivian Green graced the stage, promising to perform two old songs and two new. The first was "Fanatic," a hit from her first album, A Love Story, which reached the No. 7 spot on Billboard's U.S. Dance chart in 2003. And as promised, the next was a new gem. Although critics have described Green's music as "sad, male-bashing songs," she attempts to break from that with "I'm Not Broken," which is about a love gone wrong. "It makes you want to get up and get over it instead of wallowing over some dude," she said before setting into the upbeat tune from her latest album, Vivid.

"You didn't break my heart / You just bent it / Ain't no damage / Like it never happened," she sang over the funky live music as she and her backup singers carried out choreographed two-steps akin to The Supremes.

The 36-year-old singer saved her most popular song, "Emotional Rollercoaster," for last, a neo-soul record about the ups-and-downs of a relationship. She brought the second surprise guest of the night when Kwame arrived. Unfortunately, the producer didn't perform "Ownlee Eue," but he did announce that Green is signed to his music label, Make Noise, and thanked the crowd for "rockin' with our new sound." Kwame, who produced Will Smith's "Switch" and Talib Kweli's "Listen," is also responsible for the sounds on Vivian Green's Vivid LP.

"Y'all ready to turn up real quick?" asked Green. She was met with loud "whoos" from the crowd as she started the self-described summer record, "Get Right Back to My Baby," which samples Frankie Beverly and Maze's "Before I Let You Go," instantly evoking the feeling of a family cookout on the rooftop. "Wish I never had to let you go," she sang before the band switched to the "Wobble," baiting the entire crowd to stay in unison to the line dance.

And with the audience in full-on hype mode, it was time for the man of the hour, Avant.

The "4 Minutes" singer, who was wearing his signature sunglasses, decided to go with something familiar first. "I got your legs spread all over the bed," he crooned as the swaying crowd went along with him word-for-word.

Then he moved into his very first single, "Separated," from his debut album, My Thoughts and headed into his most recent song, "Special," from his eighth studio album, The VIII, which is set to be released on Sept. 25. "I'm telling you the truth, I need y'all," he told his fans in the audience.

The R&B singer went into another classic, "Read Your Mind," as he fiddled with the button of his pants. "I wanna get naked but this is an industry party," said the 37-year-old singer. The crowd was 50/50 on the decision. "Whoo," screamed one woman. "Oh hell nah," yelled a male videographer. Anticipation was heavy in the air as he continued to toy with the button of his pants. He undid it, and then, down went the zipper -- for two seconds at least.

"Ya'll nasty as hell in here," Avant said to the surprised and laughing audience as he re-buttoned and zipped up his white pants, tucking it under his grey sweater and necklace that read "AV."

He almost performed "4 Minutes," but the singer ironically didn't have enough time and ultimately ended the set with "Don't Take My Love Away," one of the songs he describes as something different from what's been heard in music today. "When I talk about real music, I mean songs that make you feel something. I'm tired of shake ya ass, shake ya ass," he shared.

"We should change people's definition of love," sang Avant, using a small diddly from his song "When It Hurts," to solidify his point.

As long as he continues to sing, his message on love is being heard loud and clear.

Check out Vivian Green's two-step, the surprise guests and Avant's performance below.

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