I remember seeing Robert Schumann referred to as "the other Schu," to differentiate him from Franz Schubert, in a piece of fiction about a string quartet (I can't remember the title). Perhaps William Schuman could be called the "other Schumann" or the "other, other Schu" (even though his name only has one "n").
I just discovered yet another Schumann worthy of a place next to the other "Schues." Walter Schumann (1913-1958) wrote the music for Night of the Hunter. The film is praised for its direction, its cinematography, and its screenplay, but I find the music truly effective and worthy of equal praise. It is a huge part of what makes the film great. Here's a clip:
Schumann also wrote the title music for Dragnet. (The link is to a 30-minute episode that also includes some nice vintage ads: one that has opera singer Marguerite Piazza selling Camel cigarettes, one for Dentu-Creme, to remove those cigarette stains, one for a GE blender that has a really catchy jingle, and a Chevrolet commercial with Dinah Shore and Pat Boone.)