Lucinda Childs used the technical possibilities provided by the 9 Evenings to extend the definition of dance. At the start of Vehicle, a protagonist brought the artist three buckets illuminated by light bulbs in a life-sized Plexiglas box supported by an air cushion. Childs fastened the buckets to a framework and set them swinging. Ultrasound devices were set up around the framework, which immersed the buckets in an ultrasound field. As a result of the Doppler effect, the swinging of the buckets produced a sound frequency that was audible to the human ear. The rhythm of the movements was amplified and played over the loudspeakers in the Armory. The video images that could be seen on a screen to the left of the stage were produced by sounds from a local radio station not heard by the audience. In Vehicle, Childs shifted her dancing interest to everyday objects and frequencies beyond the range of human perception: ultrasound waves became a vehicle for dance-like movements.