Picture a band on a street corner in the very Nordic north. It’s winter. To keep warm, they spool out blowsy melodies of grave gait and linearity, their authority not immediately apparent. Then, as trumpeter Verneri Pohjola and Black Motorists Sami Sippola (saxes), Ville Rauhala (bass) and Simo Laihonen (drums) gather force and daring, this singular group turns from the relatively predictable to the nearly uncontrollable, delivering a rootsy brand of free jazz bristling with ideas-and melody.

Save for the Sippola showcase, “Sax-O-Phun,” the tunes are long and fun. These young musicians play hard, even putting “Song of India,” a Rimsky-Korsakov warhorse, through rigorous and unexpected changes. Pohjola is as fast as Sippola, though not as earthy; the two challenge each other and, backed by a solid rhythm section, work up a head of great spirit.

One keeper is Rauhala’s rambunctious, moody “Vainila,” its melody yearning, its improvisation expansive. Another is the title track, named after a rare metal that burns when it contacts water. Pohjola’s melody unfolds with majestic bite, paving the way for a clipped trumpet solo; then Sippola takes over, sprinkling the tune with phrasing alternately slinky and squonky. Each man gets a solo, and the drummer’s is tantalizingly short. The tune returns to its tart, harmonic beginning, establishing this weird, Salvation Army-style band from central Finland as the real deal.