1 1/2 inch copper pipe, 22 inches long, capped, containing drywall screws.
1 1/4 inch copper pipe, 18 inches long, supporting an internal extension spring.
1/2 x 1/4 barstock, 15 inches long, clamped to 3 1/2 x 1/4 inch flatstock, 15 1/2 inches long.
1 1/2 x 1/8 x11 flatstock clamped to 1/2 x 1/4 barstock.
Played with 1/2 inch copper pipe cushioned with vinyl tubing and automobile heater hose.
When neccessary it is amplified by a piezo pickup (not pictured)