Final answer:
The Billy Eckstine band is credited with being one of the first big bands to incorporate bebop style into its music, which was significant for the evolution of jazz in the 1940s.
Step-by-step explanation:
Critics say that the Billy Eckstine band was one of the first big bands to incorporate bebop style into their arranging and soloing because it represented a musical evolution during the 1940s. This style of jazz was characterized by complex chord progressions, fast tempos, and virtuosic solos that deviated from the swing rhythms and melodic simplicity of earlier big band music. Eckstine's band included bebop innovators such as Dizzy Gillespie and Charlie Parker, who were pivotal in the development of this genre. Their contributions helped to bridge the gap between big band swing and modern jazz, making bebop more accessible to a wider audience. This integration of bebop into big band arrangements was significant because it pushed the boundaries of what was considered mainstream jazz at the time and played a role in shaping the future of the genre.