Birds and Arrows have been in flux of late, testing collaborations with guest players since cellist Josh Starmer's departure last spring. But Andrea and Pete Connolly remain a Triangle indie-folk fixture, having issued three albums in the last five years. Joining them this time out are Eric Haugen (pedal steel), Kyra Moore (banjo, fiddle) and Roger Gupton (bass). Newer to the turf of husband-wife acoustic collaboration is Greensboro's Lowland Hum, whose debut LP, Native Air, arrived this week. Daniel and Lauren Goans float magical harmonies atop exquisite pastoral melodies. Similarly styled married-couple acts such as The Innocence Mission and Damon & Naomi set the template long ago, but Lowland Hum builds upon those inspirations with enticing grace.