Documentary films had small budgets and tiny orchestras, and they paid poorly, but – compared with the composer's solitary toil at piano and manuscript – the milieu was exciting. Alwyn's passionate belief that the art of film lies in its “co-ordination of a team, director, producer, designer, cameraman, musician and actor, all working together and interlocking” had its seed in his intoxicating documentary days. This can be sensed in SOS (1941), produced and directed in the earlier part of 1940 by the young John Eldridge, who at the age of 23 had set up his own company after working as an assistant editor for Herbert Wilcox. Eldridge's well-balanced, well-edited documentary depicts the lifeboat service in Mousehole, Cornwall, but, perhaps because the pictures are less exciting than he had hoped, he depends on Alwyn's instrumental colours to paint the moods. Thus, tremolo strings, surging horns and trumpets, and ominous timpani create a sensation of gales and high waves as the film opens on a long shot of a ship riding for the shore. Subsequently, too, pictures and score are sustained for long passages without the “distraction” of a commentary. Far from palling, the continuous music track adds dramatic tension and camouflages a deficiency of sound-effects - rather in the manner of an accompanied silent narrative film. So, when fine weather finds the girls making camouflage nets and the fishermen about their business, giocoso woodwind have a little game to accompany the work, until the theme is thrown to a playful string section. Elsewhere, cymbal clashes mark a lifeboat launch, and choppy violins match flashlight signals and the puffing of a train. The film culminates in a sea rescue with a stirring timpani and brass and woodwind fanfare and fast strings mixed with wind and sea. After the completion of SOS, Eldridge joined Donald Taylor at Strand. Here his history of architecture, Architects of England (1941), called for a pastiche of musical styles reminiscent of, but less exuberant than, Taylor's earlier Of All the Gay Places. “Apologies to Mozart !” scribbled Alwyn on a section of his score.

Alwyn's belief in the co-ordination of the team could result in his placidly taking the bottom of a pecking-order of picture, commentary, and music. In the twelve-minute It Comes from Coal (1940), for example, the music is continuous but suppressed behind the spoken commentary.