Having not heard Crooked Still's first two CDs (released in 2004 and 2006), I can't tell you what the band, then and now based in Boston, sounded like when Rushad Eggleston and his cello filled the spot now occupied by cellist Tristan Clarridge and fiddler Brittney Haas. I know only that that iteration of Crooked Still got a lot of flattering press, and I read of "changes" with the new lineup, along with the reassurance that all is "still crooked."

What I do know more certainly, however, is that Still Crooked is a finely crafted, musically well-endowed disc with a charmingly idiosyncratic reading of mostly traditional, mostly unfamiliar songs (including three trad-styled originals and the late Ola Belle Reed's "Undone in Sorrow"). Crooked Still is a string band, but it has little to do with the "old-time" that usually prefaces "string band," and it has nothing to do with bluegrass by any definition I can think of.

The five band members are all -- very clearly -- classically trained. They're technically as proficient as you can get, and the sound they glean from their interaction is not quite like anything I've heard applied to folk music. There's not only a deep British/New England ballad sensibility but a subtly restrained jazz tone, plus a dazzling interplay of cello and fiddle weaving a sonic universe of its own. And there is Aoife O'Donovan's amazingly expressive voice, sometimes melancholic, sometimes warm, sometimes apparitional.

Even the rare standard songs take on a whole new character here. Only one of the titles was immediately recognizable to me -- the American murder ballad "Poor Ellen Smith," an old-time and trad-bluegrass staple -- but Crooked Still's arrangement is strikingly innovative. Likewise, the band's take on Mississippi John Hurt's rarely covered "Baby, What's Wrong With You?" borrows nothing but the words and the melody (sort of) from the source version. At least to my hearing, the most affecting cut is "Captain, Captain," an arcane variant of a gloomy ballad usually called "Drowned in the Deep Blue Sea," arranged in what feels -- even with only five instruments -- like a full orchestral setting. O'Donovan's singing is at its most emotionally piercing with dark materials like this.

Most of the time Greg Liszt's banjo resists Southern accents, as if to stress that there have always been other folk-banjo traditions than the Appalachian. Corey Dimario's double bass underscores the omnipresent sense of dread that propels many of the narratives, where lovers meet unhappy fates by death (murder, accident) or mere sad parting. On the other hand, the lovely 19th-century shape-note hymn "Florence" comforts with the assurance "Fast as you bring the night of death / You bring eternal day."

Here's to a long, rewarding life to Crooked Still, a young band carrying old traditions in good hands.