If you listen to their debut album "Thankful" with your ears and not your heart, Mary Mary doesn't differ much from other R&B girl groups on the radio. It's the twentysomething twosome's lyrics that sets "Thankful" apart from the monotonous drivetime drone. Mary, Mary, whose "Shackles (Praise You)" has hit #12 on Billboard's singles chart, is the charter act of a category Columbia Records is calling "R&B gospel": music that infuses the energy of urban music into traditional gospel. On "Thankful," the organ chords found in gospel hymns are replaced by the thumping beats of hip-hop drum machines.