They were an unlikely, one might say polarizing duo, when their 2007 debut “Raising Sand” took the music world by storm. But their “almost telepathic” connection with each other, and with producer T-Bone Burnett, worked its charm, and they’re back now, 14 years later, with another collection of intriguing arrangements of American music, covering such songwriters as Merle Haggard, Lucinda Williams, Calexico, and Ola Belle Reed.