Although the styles are quite different, there are a couple similarities in shape and overall composition. For starters, they both use a similar pallet of muted tones, both containing mostly shades of brown and red. Although Picasso's piece here is abstract and Hopper's is modernism, they both convey a similar tone of comfort and closeness. The musician piece conveys three musical artists most likely composing music together which, combined with the soft colors, makes the viewer feel a sense of peace with them as they talk. Similarly, Nighthawks also lets you "pear" into the lives of others at an almost deserted local shop. Like being in your own local store or restaurant, you feel peaceful and relaxed looking at the piece. Again, this feeling of calm is intensified by the soft colors. As for shapes, both utilize squares and rectangles, Picasso in his figure's bodies and Hopper in the buildings.
The answer among these works that features a flute with a delicate, "breathy" sound in a relatively high register is Concerto for Orchestra by Bela Bartok.
