Though I had heard of Unspoken Tradition, I had never heard the band until a few days ago when a review copy showed up in my mail. I soon learned that its first album was released in 2013.

So Unspoken is not new to those who have been following it through the bluegrass wilderness. What is new is the sound, which remains novel 13 years later. It's modern bluegrass of a distinctive sort, neither jamgrass nor anything particularly like the groups (Seldom Scene, Newgrass Revival) that delivered an urbanized approach to the genre's early decades. As a reviewer I wish I had heard what came before so that I have a clearer idea how this outfit gets to where it is on Heartwood.

Still, as the very name suggests, these five guys from North Carolina (with two guests) are respecters, if not imitators, of tradition, even if their harmonies aren't ones Bill Monroe and the other foundational artists who stepped forward in his wake would have recognized or been prepared for. Still, nothing about this doesn't feel like something that even decades ago wouldn't have been perceived as bluegrass, at least of a kind. Having taken in 'grass of all kinds since I first was exposed to Flatt & Scruggs in junior high school, I think I'd know, I hope.

One consequence of fandom in a genre is that one may end up frozen in place, defining as legitimate only the music as first it entered one's life. I still treasure the hard-core mountain bluegrass above all, but I have managed to understand that all of it can't sound that way if the style is to survive and claim new generations of listeners. It helps an oldtime fan such as the undersigned that bluegrass, though it was radical when it came flying out of Monroe's Blue Grass Boys (about 1946 in the standard accounts, in 1939 in Monroe's own, with World War II dividing the two dates), the music is inherently conservative.

That means in effect that it can change only so much before it's no longer bluegrass. That's why one doesn't often, or ever, encounter hyphenated forms that do more than locate a variety by its geographical point of departure. In short, one need not fear running into, for example, a monstrous sub-genre such as bluegrass-rock.

With each succeeding song Heartwood happily sounds ever more like its own eccentric self. The second cut is a version of a past Nashville hit, Larry Gatlin's "All the Gold in California," possibly the one moment of genius in the career of somebody I've long filed under irritating hack. The remaining seven songs range from good to outstanding, often in a melodic way one doesn't associate with a bluegrass song. (Most employ other charms to work their magic.) The highlights, for me at least, are "Cathedral Pines" (Tim Stafford & Rick Lang, an environmental anthem with a spiritual twist), "Just Call Me Lonesome" (George Ducas & Radney Foster reminding you how an ordinary country song can sound better than it is), and -- most of all -- "Barbara Allen," not only because it's a grand, hundreds-year-old ballad never to be tired of but because it's arranged so interestingly. Now there's living, spoken tradition for you.