It's not so surprising that the Roots backed Nneka at one of her first U.S. gigs a couple of years ago. The 31-year-old Nigerian-German singer excels at the type of neo-soul that the Roots and pals like Erykah Badu have been championing for years. On her second stateside album, Nneka embraces another influence: late Afro-pop pioneer Fela Kuti. Add some pop hooks and hip-hop beats to the mix, and you have a globe-hopping record that refuses to settle into one place or groove. Like 2010's Concrete Jungle, Soul Is Heavy puts a lot of weight on Nneka's raspy voice, which drives songs like "Shining Star" and "Don't Even Think." But it's the sassy brass and rolling percussion of "Lucifer (No Doubt)" and "My Home" that are at the core of Soul Is Heavy's global R&B.