Prior to 2014's highly regarded Goodnight Tender, Amy Ray had spent her career, both solo and with fellow Indigo Girl Emily Saliers, dancing around the margins of various American roots traditions. The Indigo Girls' music has always been rooted in folk, and Ray's solo albums have often taken the form of rough-hewn Southern punk and indie rock with occasional mandolins and rootsy adornments that implied her Georgia upbringing without ever really approaching anything that could be called country. When she finally let loose with Goodnight Tender, it was Ray approaching Americana in her own maverick style, borrowing bits of classic outlaw country attitude and raw mountain music and infusing it with a sort of hard-won grace and the seemingly eternal punk spirit that is her hearth fire. Following four years later in its footsteps is her sixth album, Holler, a hearty country-soul masterwork that treads similar rural routes and offers up some of the most organic and cohesive songwriting of Ray's career. Working again with producer Brian Speiser and her core live band, Holler is by and large an analog effort, recorded mostly live to tape at Echo Mountain Studios in Asheville, North Carolina. A deep roster of impressive guests like Vince Gill, Alison Brown, Lucy Wainwright Roche, Derek Trucks, Justin Vernon, and Brandi Carlile populate the 14 tracks, all lending their signature talents in a collaborative way without distracting too much from the bigger picture. More arranged and thematic than anything she's done before in her solo career, Holler begins with an instrumental prelude ("Gracie's Dawn") that is equal parts old-time Southern waltz and classic Nashville countrypolitan, introducing the sonic palette of pedal steel, strings, piano, and most notably, the big horn stacks that appear throughout the rest of the album. The heavy brass element, which adds weight and attitude to cuts like the defiant Southern identity statement "Sure Feels Good Anyway" and the raucous band rave-up "Sparrow's Boogie," was inspired by Jim Ford's 1969 cult classic Harlan County, according to Ray. The sparrow reappears later on in the beautiful ballad "Sparrow's Lullaby," while the linked "Old Lady Interlude" and "Old Lady Dreaming" furthers add to Holler's thematic element, tying the overall sequence together in interesting ways. Throughout it all, Ray's powerful voice delivers personal ruminations, affirmations, history lessons, and the fiery politicized missives and cultural reflections that come from a lifetime of activism. More than anything, though, Holler has heart and soul and its richness and depth make for one of the best releases of her career.