A. Firth, an American jazz arranger active primarily from the late 1940s through the 1970s, was a significant, albeit often uncredited, contributor to the big band sound. Known for their intricate yet swinging charts, Firth's work blended traditional swing idioms with nascent bebop harmonies. Their arrangements were sought after by numerous West Coast ensembles, and while specific collaborations are largely undocumented, their distinctive voicings can be heard in the evolving soundscapes of several prominent dance bands and studio orchestras of the era. Firth's contributions helped shape the harmonic and rhythmic language of post-war jazz band music.