P.M. Dawn were not among the first acts to mix singing and rapping, an approach that dates back to the old-school likes of the Sequence and paid off later in the 1980s for the million-selling Whodini. The method was actually approaching prevalence when the sibling duo broke through the next decade with "Set Adrift on Memory Bliss" (1991), a number one pop hit preceded by a spate of recordings that eventually provoked Billboard to retitle their R&B charts with the addition of "hip-hop." P.M. Dawn did distinguish themselves with a uniquely sensitive, introspective, and sometimes...