Wikipedia
The Feed-Drum is an imperial bass drum with a system of electronic conditioning of the skin conceived by composer Michelangelo Lupone and coproduced between CRM - Centro Ricerche Musicali, Rome and Istituto Gramma in L'Aquila.
Through the principle of feed-back, the signal produced by the excitation of the skin returns to the skin in the form of acoustic pressure. The result is an infinitely sustained sound. The system controls the damping of the movement of the skin, and therefore the decay rate of the sound, and permits isolation of high frequency modes by the combined action of nodes present on the skin and the amount of feed-back input energy. The design on the skin surface is a simplified map of the oscillatory modes based on the Bessel functions. The map was limited to 13 diameters and 8 nodal circles, the latter divided into even semicircles (to the left) and odd semicircles (to the right). See also Skin-Act.
Image: Feed2.jpg|Map of the first 13 nodal diameters Image: Feed3.jpg|Feed-drum, first map with 13 diameters and 8 nodal circles