B. Armstrong, an American jazz arranger active from the late 1940s through the 1970s, was a significant, albeit often uncredited, force in post-swing big band jazz. Known for his sophisticated harmonic voicings and intricate counterpoint, Armstrong's arrangements imbued classic standards and original compositions with a fresh, modern sensibility. He frequently collaborated with prominent bandleaders of the era, crafting charts for ensembles that emphasized a rich, full sound while allowing for individual soloistic expression. His contributions helped define the evolving sound of large jazz ensembles, bridging the gap between the swing era's dance-oriented arrangements and the more complex, concert-hall focused works of later decades.