[ross hamilton hill]

Ravens do call at night but only just before dawn, and then very rarely. I listen closely to raven calls and the long mournful sound is used to make the call carry, when crows ( sorry, we call them crows never ravens ) are close together their calls are much crisper, and more complex. While the overall sound is sombre, once you listen carefully to the changes in tone and duration, you can discern gleeful calls, excited calls etc.
I also recall but have no citation that the raven in Egyptian mythology was sacred to the sun God Ra because being a scavenger the raven cleaned up the world's left-over debris, the sun drying up and destroying in the same way.
I don't have a problem with the raven being a bringer of good tidings, they are the most intelligent of birds and easy to tame and really quite timid.