Keyser, an American jazz arranger active from the late 1960s through the 1980s, was a significant, albeit understated, force in large ensemble jazz. Known for his sophisticated harmonic palette and intricate counterpoint, Keyser's arrangements blended post-bop sensibilities with a refined orchestral approach. He frequently collaborated with prominent big bands of the era, crafting bespoke charts that showcased individual soloists while maintaining a cohesive, swinging sound. His contributions are particularly noted in his arrangements for several uncredited studio recordings, where his innovative voicings and dynamic contrasts elevated the material, subtly shaping the sound of modern jazz big band music for a generation.