Canadian indie outfit Cowboy Junkies have spent 30 years putting forth a nebulous blend of plaintive folk, classic country, acoustic blues and psychedelic rock, releasing more than a dozen records along the way. The group’s placid music is often lumped in with the slowcore sound of the 1990s, though it’s more earnest Americana than detached gloom. The Junkies’ most recent release is the Notes Falling Slow box set, which collects the band’s first three albums of the 2000s, plus a bonus disc of unreleased material from the era. At the Georgia Theatre, they’ll play tunes from 1996’s Lay It Down, plus a set of songs by Athens’ late Vic Chesnutt, with whom the group collaborated in the past and fêted with the Demons cover album in 2011.