Trumpeter Lina Allemano, who divides her life between Toronto and Berlin, is one of Canada’s most prominent—and hard-working—experimentally inclined jazz musicians. The Diptychs is the eighth recording by the quartet she first assembled twenty years ago with alto saxophonist Brodie West, bassist Andrew Downing, and drummer Nick Fraser. The six tracks here, all composed by Allemano and arranged in three musically related pairs (hence the album’s title), offer persuasive evidence of the benefits of working over the long haul with a fixed group of musicians. The album feels thoughtful and unforced, as much concerned with texture as with notes and rhythms. Downing, bowing his bass more often than plucking it, will play long sustained tones or lurching ostinatos. There’s plenty of improvisation, but hardly any soloing. Now and then a scale-like figure or a concise, scene-shifting melody emerges, played in unison or harmony and clearly, if inconspicuously, composed. The opening track, “Positive,” begins with attention-grabbing octaves ping-ponging between sax and trumpet, followed by some joint improvisation—not unlike how Ornette Coleman and Don Cherry used to interact—while Fraser, by turns, swings and clatters gracefully. (Only a drummer as imaginative and nimble as Fraser can be said to clatter gracefully.) As the following “Negative” begins, Allemano and West hold fast to a dissonant pair of notes before getting into a friendly squabble and then resolving their differences in a calmer mood. Throughout the album, similar non-formulaic principles apply. If the precise nature of the musical relationship between the dual pieces of each diptych remains enigmatic even after several hearings, all the more reason to keep listening.