For a group that earned its reputation for the confessional nature of its debut album (2006’s Declare A New State! was written and recorded as the duo broke off, then resumed, a romantic relationship), the L.A.-based Submarines have returned with a surprisingly sprightly sophomore effort. The direct, insistent choruses of songs such as “Maybe” seem to be crafted solely for their sing-along ease, while even the more brooding numbers (“Fern Beard”) are buoyed by singer Blake Hazard’s light-as-air voice. Things come together most effectively on “Thorny Thicket.” The song relies on copious amounts of glitchy electronica and warm, analog keyboards, over which Hazard and husband John Dragonetti (former frontman for Boston alt-rockers Jack Drag) wend their way through soaring harmonies about love in a way that’s either blissfully happy or perversely ironic. It’s a unique admixture of the serene and the sappy, of pop formality and contemporary experimentation, making the Submarines notable for more than just their romantic backstory.