|Inspired by Noh, the major form of classical Japanese musical drama that has been performed since the 14th century.
The Noh masks are used to portray female or nonhuman (divine, demonic, or animal) characters.
Several types of masks, in particular those for female roles, are designed so that slight adjustments in the position of the head can express a number emotions such as fear or sadness due to the variance in lighting and the angle shown towards the audience. With some of the more extravagant masks for deities and monsters, however, it is not always possible to convey emotion. Usually, however, these characters are not frequently called to change emotional expression during the course of the scene, or show emotion through larger body language.
The rarest and most valuable Noh masks are not held in museums even in Japan, but rather in the private collections of the various heads of Noh schools; these treasures are usually only shown to a select few and only taken out for performance on the rarest occasions. This does no substantial harm to the study and appreciation of Noh masks, as tradition has established a few hundred standard mask designs, which can further be categorized as being one of about a dozen different types.
Source from: wikipedia.org