If you want someone’s attention, whisper – so goes the old commercial trope. And if you’re going to make that work in music, you’d better be astoundingly good. Fortuitously, singer/songwriter Joshua Radin is. His lush new album “Underwater” (Mom + Pop Records) is arresting, even though Radin’s voice rarely rises above the volume of a murmur, drawing you into a moody sonic universe that is both quiet and entrancing. Radin plays at 7:30 p.m. Wednesday at Carolina Theatre in Durham, on a bill with A Fine Frency. Tickets are $26. See carolinatheatre.org for details.