I found a simple definition of Harmony : A pleasing combination or arrangement of different thing.
The chemical or petrochemical plant layout is concerned with the spatial arrangement of processing equipments, vessels, pipes, workplace, and also warehouse. A good layout must ensure that the plant functions correctly, safely and efficiency. So it considers the design constraints arising from safety, environment, construction, maintenance, and operation with economical balance.
We, engineers, call it : Harmony.
It’s absolutely true that harmony is not only about music.