Music and Darkness

It is common knowledge that light and dark are opposites, but only the vastly uneducated thing that light is the only way to protect yourself from darkness. It is the most efficient one by far, but not the only one.
Music plays a large role in keeping the darkness at bay. A rousing song into the black as the cleric struggles to get a lantern lit somehow wards off the sudden influx of darkness on the people stranded. It won't last long, but as a last ditch measure, it is enough.
As such, those who can play with feeling are highly sought out in both civilised areas for extra dark protection, and for adventuring parties that will venture out into the dark. Families will teach children the songs of their people no matter how talented, for it is the feeling behind the song that drives the darkness away. A song or a tune with no feeling will have little to no effect. Many people have tried to narrow down the term "with feeling" into something more concrete but after all these years, no one has thought of a better term with how the process goes.
Bards word magic such as Vicious Mockery and any music they play also has an effect against creatures of darkness. This makes bards just as coveted as clerics, and they are a popular adventuring choice.