The didactic side of this classic documentary has to do with how over-cultivation plus drought were turning millions of acres of the Midwest into a dust bowl. But not to worry - the government is on the case. The desolated farmsteads, the procession of heavy-laden jalopies along the highway, the migrant camps: this is The Grapes of Wrath, actuality version. Lorentz's self-consciously poetic manner and the declamatory style of his commentary ('Blown out! Baked out! And broke!') now seem the very essence of the New Deal '30s. But the most forceful element is the music, with Thomson reworking such hackneyed material as 'Streets of Laredo' and 'Mademoiselle from Armentières' into one of the greatest and most influential of film scores.