Lakeshore Records has offered up this interesting interview with Theodore Shapiro, the composer of TRUMBO's Original Score.
Shapiro explains how the music of the period, particularly jazz, influenced his compositions:
What I wanted to do was to take elements of the period's style - some of the language of jazz and the harmonic ideas - and use those as an ingredient in something that felt a little more modern...
Shapiro goes on to explain how his orchestrations referenced the Big Band sound of the era while also experimenting with "prepared piano" techniques. He also reveals his most challenging and favorite scene to score.