Quercus was born from the lineup that appeared on June Tabor's stellar At the Wood's Heart from 2005.

Huw Warren, her longstanding pianist and musical director, invited saxophonist Iain Ballamy (who records for ECM with his group Food), whom he had played with previously in various live settings.

Both men are seasoned jazzmen and improvisers.

The trio hit it off and toured, developing new material as they went.

This date was captured live in 2006.

Obviously, this is not a jazz record in any normative sense.

But this doesn't mean that jazz doesn't make its presence felt on these strikingly adapted traditional songs and standards.

Of course, given that Tabor is the greatest living British folksinger, the music of the Celtic and British Isles traditions informs virtually everything here.

On Robert Burns' "Lassie Lie Near Me," Tabor offers her completely empathic, autumnal read of the poet's lyric, Ballamy follows her as a second voice, following the melody and shifting its accents to draw the listener in closer.

On the instrumental break, he and Warren engage in brief yet gorgeous interplay.

William Shakespeare's "Come Away Death" begins almost as a drone chant, with only the singer and saxophonist.

When Warren enters, he does so haltingly.

Tabor completely carries the melody; she fully inhabits the lyric and brings us inside it as Ballamy illuminates the subtleties in its meaning.

Warren enters halfway through and engages him in winding through the simple chord structure and the pair engage in shimmering, emotive improvisation.

On George Butterworth's setting of A.E.

Houseman's 1896 poem "The Lads in Their Hundreds," the pianist introduces Tabor.

Her smoky, restrained delivery carries within it all the melancholy of the world, despite the sweet song melody.

Warren's economical arpeggios are graceful, elegant, and Ballamy falls in beside him in the break, offering his horn as a vocal counterpart.

"Teares" is a glorious piano solo, while "Brigg Fair" is mightily performed by Tabor a cappella.

The Mack Gordon/Harry Warren tune "This Is Always" is the only jazz standard; she's not always been successful at interpreting them, but she nails this one while radically revisioning it.

The one contemporary song, David Ballantine's "A Tale from History (The Shooting)," is the only track here performed without rearrangement; the songwriter should, however, just turn the song over -- this group's performance is definitive.

There are a couple of British pop tunes here in Les Barker and Yosef Hadar's "Who Wants the Evening Rose" and in closer "All I Ask of You," a torch song that Ballamy and pianist Django Bates adapted from Gregory Norbet's melody for their 1990s band Loose Tubes.

That said, Tabor's performance renders all previous versions as building blocks for this one.

From the pristine recording quality to the stirring, poetic performances, Quercus is exceptional.

One can only hope this is not the last installment for this group, and, if so, that Tabor and Warren appear on ECM more often.