Every now and then a certain Nova Scotian fiddler descends upon our town, boards the Ark, rips the veil, and stands us on our ears. Ashley MacIsaac accomplishes this by whipping up strathspeys, reels, and jigs with astonishing dexterity, which is what one ought to expect of any strongly steeped Cape Breton fiddler. The turning point comes when he grinds his instrument like a Scot, increasing the friction so the bow goes frowsy with flyaway strands.

MacIsaac’s relationship with his Celtic heritage is beautifully embodied in “The B Flat Cloggs,” an even-tempered step that steadily evolves into the punchy hornpipe that generations of children have associated with Popeye the Sailor Man. We’re not talking about the brassy cartoon fanfare that resounded whenever a can of spinach popped open. The tune in question is a lively sunburnt mariner’s dance dating from the eighteenth century or earlier. By the time Ashley launches full throttle into the familiar hornpipe, anyone susceptible to this kind of energy might feel the urge to howl and pound the floor with both feet.

Have you ever encountered a musician whose ability to manifest dark and uncompromising currents of raw energy made your hair stand on end? You may have been experiencing the presence of what poet Federico Garcia Lorca called the duende, a cathartic spirit that drives artists far beyond accepted notions of conventional entertainment. Janis Joplin was volcanically in touch with her duende. The same is true of saxophonist Pharoah Sanders and of Ashley MacIsaac.

During the 1990s, MacIsaac attracted a lot of attention as the Canadian counterpart to contemporary Celts like England’s Eliza Carthy and Duncan Chisholm’s Highland folk rockers, Wolfstone. Ashley was a wild card, capable of fiddling with almost frightening fervor yet stylistically impossible to confine or categorize. He played piano and sometimes sang a little like Bob Dylan or Lou Reed. Then a reel delivered with dazzling exactitude would begin to seethe with drum loops, techno glitches, and bursts of electronic sampling, as if he were fiddling at a late-night rave in Detroit.

Ashley’s temperament brought him notoriety, and he somehow made it through the perils of excess. The best thing about surviving one’s youth, other than being able to say to yourself that you’re very glad you forgot to die, is the way the fruits of experience and painstakingly acquired abilities come to represent a different sort of creature descended from the one who danced relentlessly along the razor’s edge years ago. While we don’t know exactly what kind of a show Ashley MacIsaac will bring to the Ark on July 1, the evidence suggests a strong-as-ever bond with the fiddling tradition around which his life has always revolved.