1. At the movies

One could say that composers were already wrestling with the demands of Socialist Realism before the name was invented or the party policies consolidated. The constraints were instead provided by the film industry, where composers had to score films on short schedules, in subordination to dramatic demands over which they usually had no control, and to the satisfaction of a much broader audience. Both Prokofiev and Shostakovich thrived under these challenges, even though they sometimes downplayed the seriousness of their efforts in retrospect. Shostakovich began composing successful works for film very early in his career. In A Girl Alone (1931), featuring an opening exotic motif driven by a phlegmatic bassoon, a young Leningrad teacher is sent to work in the remote Altai region, where the natives resent the shepherding labor lost from having to send their children to school:

  

The teacher quickly wins over the children and lets go of her bitterness. The adults, of course, eventually come to see the error of their ways and to appreciate the importance of (Soviet) education. Directed by the founders of the Factory for the Eccentric Actor, the film score incorporated a more satirical approach than would later be deemed acceptable, as you can hear in Shostakovich's depiction of the Chief sleeping and awaking:

  

Enjoy this polka from The Age of Gold ballet suite (1930), brimming with with, irony, and elements of parody: 

  

For a much more ambitious film collaboration, listen to Prokofiev's score for Eisenstein's Alexander Nevsky (1938): 

   

Prokofiev had returned to the USSR for good in 1932, and he soon made his peace with the mandate of Socialist Realism. Pronouncing himself ready to compose "lightly serious" and "seriously light" music that would be accessible to a larger audience, Prokofiev largely succeeded with this film score. He subsequently worked with Eisenstein on the score for Ivan the Terrible as well. If you're curious, listen to the introduction: 

   

Shostakovich similarly contributed the score to an early example of kinoleniniana—films about Lenin. In The Man with a Gun (1938), an ordinary soldier has a life-changing encounter with Il'ich, and Shostakovich's arrangements proved quite popular: