The covers album is a tricky old beast and one that few acts manage to fully tame.  It’s an endeavour that can easily expose a lack of direction, an absence of fresh ideas or worse still, an ill-judged excursion into self-indulgence.  It’s no small miracle, then, that female-vocal-bluegrass darlings The Wailin’ Jennys have made such a coherent success of Fifteen, their first album since 2011’s highly acclaimed Bright Morning Stars.