Harmony and melody, hopefully this helps :]
It is an ideal case of the Neoclassical style. Neoclassical design is a structural style delivered by the neoclassical development that started in the mid-eighteenth century. In its purest shape, it is a style chiefly got from the engineering of traditional artifact, the Vitruvian standards, and crafted by the Italian modeler Andrea Palladio.
Answer:
A diminished interval has one less semitone than a perfect interval. Since C to G is a perfect fifth (7 half steps), C to Gb would be a diminished fifth (6 half steps). Since C to G is a perfect fifth (7 semitones), C to Gb would be a diminished fifth (6 semitones).
