Amsterdam improvisers John Dikeman and Jasper Stadhouders bring their aggressive attacks to Chicago to collaborate with a raft of local players

In the fall of 2016, I was in Amsterdam for the October Meeting, a festival of young Europe-based improvisers. As the three-day event ended and a partylike vibe took over, saxophonist John Dikeman—an American living in the Netherlands—decided that he needed a haircut.…