"What is this music?" Fundamentally, it's an exploration of what happens when an improvisatory instrumental voice (saxophone) is placed into the world of early vocal music, which has elements of both improvisation and formal structure. In reality, it's an adventure in which the four male voices of the Hilliard Ensemble travel the 14th and 15th-century territory of Morales and Dufay, visit the 12th-century Pérotin and roam even earlier ages of plainchant, accompanied by the always sensitive and tasteful, often astonishing, saxophone improvisations of jazz master Jan Garbarek. Sometimes, these new melodies simply accompany; sometimes they transform the common--a routine minor chord, for instance--into a sublime, indescribable moment. The answer to the above question is easy, but it's different for each listener. --David Vernier