The music composed for the Shifting Ground installation (1992) is controlled by a detector that monitors infrared changes in the central area of the installation.  As spectators move through this area, the detector turns a switch on and off.  This switch then activates a drum machine, subsequently sending MIDI (Musical instrument Digital Interface) information to a Macintosh computer running a program I designed using the MAX programming language.  When this program is running, the computer generates a response on a synthesizer each time it receives one of the MIDI impulses from the drum machine.  The detected motion either starts a random sequence of notes, turns off a random sequence of notes, or randomly selects a new group of sounds to be used.  The synthesizer contains sixty-four possible combinations of sixty-four sounds which I designed in response to the visual images.  I would especially like to thank Dr. John Comfort, who taught Computer Science at Florida International University.  He designed the infrared detector as well as the circuit board and switching mechanism that links the detector to the Macintosh computer.  The interactive element of this installation would not have been possible without his generous assistance.