In Brief

* * * Wreckx-N-Effect, “Hard or Smooth,” MCA. “Rump Shaker,” this album’s hit entry in rap’s burgeoning cult of the derriere, and “New Jack Swing,” a kick-in-the-head remix of Wreckx’s 1989 dance hit, are just two examples of how the brawny but musical rappers Aquil Davidson and Markell Riley rock the party. The producers, including Markell’s brother Teddy, contribute raw dance grooves, tasty synth effects and grinding, up-front hip-hop beats.