I made the Time Harp in the spring of 2008 for the annual Garden of Memory event at the Chapel of the Chimes in Oakland. As someone walks near the piece, one or more of the four motion sensors positioned near the top of it kick on, which activates a motor that grinds a plastic coffee lid into a tightly stretched nylon string. There is a contact microphone (piezo) fixed at the base of each of the four strings. The signals from the contact mic are fed to a mixing board and amplifier.
The interactive nature of the motion sensors seems to invite the audience to dance with the piece.
I also used the piece for Time Sensitive Materials, a two person show with Bodil Fox at Cricket Engine Gallery, also in Oakland, September, 2008. In that incarnation, it was not controlled by motion sensors, but by a record player. The records had shapes cut out of copper sheeting glued down to them, and had live wires leading to the four rotating coffee lids stuck through the dust cover of record player, so as to act as switches. As the record spins, it would switch the the motors of the harp on and off, and thus control the music.