The Depression and the arrival of synchronized sound had a profound impact on documentary film practices. The modernist aesthetic that had characterized the important documentary work of the 1920s gave way to a new emphasis on social, economic, and political concerns. This shift is symbolized by the career of Joris Ivens, who made short, aesthetically innovative documentaries in the 1920s and then, after a visit to the Soviet Union in 1932, shifted to politically committed works such as Borinage ( 1933), about the oppressive living conditions of miners in Belgium. While documentaries of the 1930s often challenged the policies and politics of established governments, many film-makers in the west and in Japan developed new ties with governments during the decade, often to make films advocating progressive goals. These ties were further developed during the Second World War, as documentary played a crucial propaganda role on both sides of the conflict. During the 1930s and 1940s documentary increasingly became a form that reached and influenced mass audiences for purposes beyond entertainment or art.
The shift from live audio accompaniment to recorded sound came to documentaries later than to fiction filmmaking, though there were some early and important exceptions. Warner Bros. used the Vitaphone to film vaudeville acts in 1926 -- short subjects that had documentary value but were soon interpolated into larger fictional frameworks (e.g. The Jazz Singer, 1927). Fox Movietone News appeared in 1927, using synchronous recorded sound to film events such as the departure of Charles Lindbergh. As the mainstream industry switched over to synchronous sound, silent cameras flooded the market at little cost and were sometimes acquired by aspiring documentary filmmakers. In many instances, the introduction of recorded sound meant that documentary film-makers reapplied the basic format and techniques of the illustrated lecture-- narration, music, and sound effects laid over images shot with a silent camera. Recorded sound allowed not only for greater standardization but also for greater precision and complexity in linking image and sound. Innovative filmmakers like Alberto Cavalcanti pushed these new possibilities in experimental directions. Moreover, in the 1930s a few film programmes initially presented with live narration and/or music had a synchronized sound-track added, including Luis Buñuel's Las Hurdes (Land without Bread, 1932).
The explorer-adventure-travelogue genre remained highly popular throughout the 1930s. A theme running through many of these was the challenging but triumphant deployment of western technologies in underdeveloped or inaccessible areas. With Byrd at the South Pole ( 1930) traced the plane voyage of Byrd across Antarctica, and The Mount Everest Flight ( 1933), an illustrated lecture by Air Commodore P. F. M. Fellows, depicted 'the official story of man's Conquest by Air of one of the last of the world's explored areas'. Osa and Martin Johnson released Congorilla ( 1932), which included a few scenes among pygmies of the Belgian Congo (Zaïre) shot with synchronized sound. Western arrogance, American racial imagery, and the Johnsons' churlish humour were particularly evident in one sequence: Martin gives a cigar to an unwary pygmy, who smokes it until becoming ill. With African adventure traditionally seen as dangerous and primitive, the presence of the diminutive and attractive Osa added a new twist to the safari film. The heterosocial realm of tourism was added to the homosocial world of male adventure, changing the dynamic. Osa provided a needed element of vulnerability and danger even as the 'dark continent' was being successfully colonized and tamed.
La Croisière jaune ('The yellow cruise', 1934) was a French counterpart to the Johnsons' productions. In effect Léon Poirier (continuity and montage) and André Sauvage (director of the Motion Picture Division of the expedition) were making a promotional film for Citroiên car technology; the expedition started off in Beirut and planned to travel to Peking and back. Driving posed few challenges, except that the adventurers decided to take their cars over the Himalayas, which meant disassembling the cars and having native Sherpas carry them through mountain passes. Western technology provided the narrative drive, while native peoples alternately provided exotic spectacle and the labour necessary to execute the rather foolish undertaking. George-Marie Haardt, leader of the expedition, died on the return trip-testimony to the ordeal and self-sacrifice of the adventurers.