For trombonist Wolter Wierbos, it’s all about fluidity: of tone, and time, of line and strategy and setting. It’s been said he can sound like a whole Ellington trombone section, from plunger-muted ya-yas to gorgeous melody statements, to dark shadings in the corners. He improvises free-associative solo concerts that suggest still more avenues to investigate. Even in composed music, he may improvise—might make up a better trombone line than the one written for him. No wonder he’s a 30-year linchpin of Misha Mengelberg’s ICP Orchestra, where the players are always re-arranging the tunes. But he’ll always nail a part if the harmonies depend on it. “I see myself as a sort of sculptor or painter,” Wierbos says, “putting sound, rhythm and form into the music. This mostly happens very intuitively and on the spot. My range goes from totally improvised music to material that’s mostly written out. The music I like to play most has a lot of my own invention in it—and improvised forms, the principle of instant composing. When music is 100% written out, I lose interest.” For a quicksilver player, he’s had long tenures in the co-op Available Jelly, and the bands and orchestras of Gerry Hemingway, Maarten Altena, Guus Janssen, and Sean Bergin. The groups he puts together for concert presentations at dOeK festivals (or his Amsterdam houseboat concerts) may improvise from scratch, or he may invite himself into another composer/performer’s concept: the rhythmically fiendish guitarist Franky Douglas, or the Moluccan-Dutch singer Monica Akihary. “Communicating with my fellow musicians, that’s the whole idea. I try not to be a show-off. Musical communication in improvised form is very difficult, and calls for a lot of openness from the players. It’s always work in progress. With some musicians it’s easy because you speak the same language. With others it’s almost impossible—but even then it can be an adventure.” Kevin Whitehead