Each mine had a steam engine, for pumping and operating the lifts. The steam whistles started being used to sound the schedule for the day. The morning whistle to start, the lunch whistle for break, then the final whistle of the day. The surrounding towns soon became accustomed to the schedule, as the whistles could be heard throughout the valley. With the different mines each having their own whistle, and each whistle having its own unique sound, as the individual notes from the mines rose in the air a chord would sound. 
This could be called the song of the valley. But occasionally. An unscripted note would break the melody. There’s been an accident, an explosion, or a collapse. come quick. And some wives would say “Thank God, it’s not his mine” While others would say, “Oh God, not him”