“oct p/a/s” (Hassui-kyo) is a piece that was presented at the Tamagawa artline project / artline week 2007, a public art project having each station of the Tokyu Tamagawa train line as it’s exhibition ground. The piece is a grandiose expression of the Tamagawa River, a regional symbol; the ancient tombs located around its basin; and also the activities between people and the natural environment surrounding this area. It is a sound installation that uses water as a metaphor of people, dynamically linking the process of a single drop of water developing into a river and reaching the sea, to the traffic of people using the train station. The sound of the water drop used in this piece was actually recorded at the source of the Tamagawa River. Eight speakers were set in a single space nearby a ticket gate and were controlled by a multi-channel audio processing system originally developed by Karesansui soundings. Four of the speakers made the “Sound of the Sun,” which follows the movement of the sun, and four of the speakers made the “Sound of Water.” A sensor program that detects the speed of people moving in an area drawn on the floor in the shape of an ancient tomb was also introduced into this system.