She surfs; she sings; she would probably look much better than most of us in a J. Crew catalog. Is it too simplistic to say Tristan Prettyman is the female Jack Johnson? Not really, because the music itself, on Twentythree, is that simple: husky, pleasant Introspection Lite. To give her credit, the San Diego native doesn’t seem to be aiming for anything more than agreeable coffeehouse (or yoga, or brunch. . .) atmospherics. Which is good, because that’s just what she gets.