Final answer:
Radio broadcasting was the mass communication force that first popularized big bands in the 1920s, surpassing other media forms like newspapers and magazines in terms of its cultural impact and reach.
Step-by-step explanation:
The force in mass communication that first powered the popularity of big bands as "name" bands was radio broadcasting. During the 1920s, radio became a main source of entertainment and news for the American public, providing a shared experience that could reach a vast audience simultaneously.
The broadcasting of big bands over the radio airwaves significantly contributed to their national fame and the shaping of a mass culture. This period experienced a surge in newspaper and magazine circulation, but radio's influence was far more extensive, permeating American homes and impacting entertainment, advertisement, and popular culture in unprecedented ways.