Mark Humphrey/Associated Press Kimberly Schlapman of Little Big Town. The band enlisted a new set of collaborators for its latest album, "Tornado." Capitol Nashville Precision has been Little Big Town's hallmark: four singers preoccupied with harmony who see it as the highest achievement, over nuance and elegance and sometimes songcraft. It has been suffocating, this approach, especially as peer groups like Lady Antebellum found prettier - and more commercially successful - ways through similar thickets. Not that Little Big Town isn't stubborn in places on "Tornado," its fifth album. At the beginning of "Front Porch Thing," its set of voices arrives unadorned, and in union, and in force. But then something unusual happens: when the music kicks in, it's gritty and slithery, not put in service of the voices but destabilizing them. This isn't quite a new template, but "Tornado" does turn out to be Little Big Town's least predictable album. The group - Karen Fairchild, Kimberly Schlapman, Phillip Sweet, Jimi Westbrook - is now less reliant on its assault of harmony, maybe because it has worked with the producer Jay Joyce, who is new to it and has turned over a significant portion of the songwriting, as compared with earlier albums, to others, notably to Natalie Hemby and Lori McKenna. Ms. McKenna, in particular, is a stretch; a well-regarded singer-songwriter who did wonders for Faith Hill a few years back, she has a bit too much gravitas for this crew, especially on "Sober" and "Your Side of the Bed," which push Ms. Fairchild and Ms. Schlapman to emotional depths they outright resist. They're better on the sultry "Pontoon," which recently became the group's first No. 1 country hit, and also on "Tornado," a muscular story of a scorned woman: "I'm a tornado, looking for a soul to take." On "Pavement Ends," again, the music is loose and powerful - when this group cedes control, it improves vastly. A sense of compromise truly settles in on the album closer, "Night Owl," which cleaves the traditional group harmony into two, men versus women. It sounds like a statement of purpose, and it's also ecstatic, with some of the outright joy of holiday music. Maybe it's a message.