Craig, you said ........" I also thought of
the sculpture in front of the Hirshorn (spl?) Museum in Washington. Its a
huge thing with three prongs that move gently back and forth. Maybe
someone else knows the artist who did this piece?"
Although I'm not familiar with the piece, it sounds like work by Harry
Bertoia, a Pennsylvania artist, whose work certainly fits the "motion"
description and adds the dimension of sound.