Throughout the film, Franz Waxman (who won a well-deserved Academy Award for scoring in this film) gives us the classics, whether onstage with the orchestra or in background music. The opera Carmen makes its presence known several times, signaling the inevitable doom of any romantic relationship onscreen; "Liebestod" from Tristan and Isolde is on hand in a sweeping, dramatic Crawford scene.
Garfield wasn't great on the strings, so the violinist you actually hear is Issac Stern. Stern (whose playing you hear in the film Fiddler on the Roof) is noted for his distinctive, strong, insistent fiddling, almost as if he could saw the instrument in half. It's perfect for the rawness that Garfield brings to this humble-man-makes-good role. You will see Stern's fingers in close-ups of the violin.
Waxman gives Garfield's rough-hewn man sophisticated music and places many of the pop songs, the mass art, as incidental music behind our sophisticated leading lady.
You will hear pop culture music playing prominently in the background. After Crawford and Garfield first meet, there is the tune, "I Guess I'll Have To Change My Plan." It's a Schwartz and Dietz breakup song, which, like Carmen, foreshadows doom right from the beginning. ("I guess I'll have to change my plan./ I should have realized there'd be another man.") Later, Gershwin's "Embraceable You" tortures Crawford as she sits in a lonely bar, far from the one she loves.
During production of this film, the legendary actress would win an Academy Award for her role as the beleaguered mother in Mildred Pierce. In Mildred the year before, Crawford is the titular character who is the voice of reason with good intentions throughout. Humoresque, comes on the heels of that, showing Crawford's range. In this film, the actress plays a selfish, unfaithful woman who is something between a supporting character and leading lady, in terms of time onscreen . (Her appearance starts at about 20 or 30 minutes into the film.)
She's also a side character is everyone's life. If music is Garfield's love, then Crawford is the "other woman."
Humoresque is recommended if you wish to listen to music which is integral to the plot and watch a three-hanky story filled with unrequited love and operatic tragedy.