Kenton Dectet #390, a significant figure in post-war American jazz arranging, emerged in the late 1940s. While details of their nationality remain elusive, their distinctive style, characterized by intricate voicings, dynamic contrasts, and a sophisticated harmonic palette, left an indelible mark on large ensemble jazz. Their work, often associated with the progressive jazz movement, pushed the boundaries of big band sound, moving beyond traditional swing arrangements. Dectet #390's contributions are primarily recognized through their innovative charts for various uncredited ensembles, influencing a generation of arrangers and shaping the evolution of jazz orchestration during a pivotal era.