(Rhino/Warner Music)

When Billboard bestowed its coveted Century Award on Emmylou Harris in 1999, the magazine declared her a "truly venturesome, genre-transcending pathfinder". Don't take their word for it; all you need to do is consider the list of artists that the 60-year-old icon has worked with. Impressive as her breakout '70s collaborations with Gram Parsons might have been, she's since teamed up with everyone from Johnny Cash and Neil Young to Chrissie Hynde and Bright Eyes.

Accompanied by revealing liner notes that are roughly the size of a small-town telephone book, the four CD/one DVD Songbird lives up to its subtitle. Knowing that the last thing her fans need to see here is "Boulder to Birmingham", Harris instead digs deep into the vaults for "The Old Country Baptizing", a vintage radio cut that finds her and Parsons sounding like they just fell out of the Louvin Brothers' family tree. Spread across the four never-less-than-classy CDs are 12 previously unreleased tracks, as well as plenty of revelatory material even Harris obsessives might not recognize on first listen.

Whether veering off into the Americana darklands with Dr. John on "Ashes by Now" or sounding like last call in '60s Nashville on the Beck duet "Sin City", Harris leaves no doubt that classic, no-bullshit country runs deep in her veins. But it's when she steps away from the genre that's now abandoned her­ that this legend proves country is a tag that's never quite fit her. If tracks like the synth-buoyed Daniel Lanois collaboration "Lost Unto This World" leave you scrambling for a description for Harris, "genre-transcending pathfinder" is a great place to start.