The soundpost and bass bar are components of the internal construction. The materials most often used are maple (back, neck, ribs), spruce (top), and ebony (fingerboard, tailpiece). Exceptions to this include less-expensive basses which have laminated (plywood) tops, backs, and ribs, and some newer mid-range basses made of willow. These basses are resistant to changes in heat and humidity, which can cause cracks in spruce tops. Plywood laminate basses, which are used in music schools, youth orchestras, and in popular and folk music settings, are very resistant to humidity and heat, as well to the physical abuse they are apt to encounter in a school environment (or, for blues and folk musicians, to the hazards of touring and performing in bars).