To hear an Oriole sing May be a common thing- Or only a divine." This means that the song of the bird can be taken as a normal, everyday occurance or you could see it as something holy, beautiful, and divine.The lines "Is of within" and "No Sir! In Thee!" imply that this decision is made within oneself.Basically, it means beauty is in the ear of the beholder, similar to the expression beauty is in the eye of the beholder.