Drummer Joe Hertenstein defines polylemma as “a choice from multiple options, each of which is (or appears) equally (un-)acceptable or (un-)favourable.” He then applies the term to one of his compositions here and also to the group, a quartet of European musicians—Germans Hertenstein, quarter-tone trumpeter Thomas Heberer (best known for his subtle presence in Amsterdam’s comic and explosive Instant Composers Pool), and bassist Pascal Niggenkemper, plus the Belgian bass clarinettist Joachim Badenhorst—whose paths have intersected in New York in the past three years, building on previous associations. Rooted in free jazz, the four explore various ways of combining composition and improvisation with techniques that include unusual meters, twelve-tone rows, graphic notation, and such interactive prods as Hertenstein’s Sugar’s Dilemma, in which individual musicians complete one another’s phrases. The composers Hertenstein and Heberer consistently construct materials that challenge and inspire each other and their partners. Among the highlights on this CD are Heberer’s Garden, an extremely quiet piece distinguished by continuous movement, and Hertenstein’s Crespect, in which improvisation and composition constantly interweave. There are multiple lines of affinity here, Badenhorst and Niggenkemper contributing as much as the composer to the ultimate realization of a dense and spontaneous work such as Stratigraphy, with Polylemma ultimately constructing a distinct group idiom.