Somehow one doesn't feel quite so alone. I'm sure that when we look at it with the eye of logic, singing doesn't really have any real impact on darkness. It doesn't really change the darkness. But the singing does change us. Singing more than any other human activity penetrates our whole being.
Music gets at our emotions, as well as our logic.
Certainly singing doesn't seem like much of a power in our world which is overwhelmed with darkness. It is not only the shorter days and longer nights of nature that change our psyche. It also is the overwhelming sense that our world is careening beyond our control. We re not in control. No one seems to be in control.