Imagine Bernadette Peters with a persistent head cold and you come close to approximating the unique appeal of former Once Blue frontwoman Rebecca Martin. On her second solo collection, Middlehope (Fresh Sound New Talent), Martin tempers Peters’ girlish trill with a smoky raggedness for singularly satisfying results. Though two of the 10 tracks-“The Sweetest Sounds” and “Ridin’ High”-are spoiled by overpowering arrangements that drown the delicacy of Martin’s voice, the balance of the album is sublime. Mercer’s “Midnight Sun,” so often treated with the chilly purity of an unsullied snowdrift, is imbued with a jagged fervor that’s mighty refreshing. Befitting Lorenz Hart’s guardedly optimistic lyric, “Bewitched” becomes a cunning blend of wide-eyed expectation and jaded pragmatism. Jobim’s “Dindi,” so often entombed in dirgelike solemnity, is charged with scorching romantic electricity. The album’s one distinct oddity is Lionel Bart’s wounded sparrow of a show tune “Where Is Love?” where Martin seems to transit the whispery vocal spirit of featherweight ’60s icon Claudine Longet, breathily pushing the sticky Oliver! ballad into the high-camp camp.