Singing Rod (3D40.20) Location: 69-R Concept/Purpose: Standing sound waves. Procedure/Explanation: The singing rod is a long, thin aluminum rod that is used to demonstrate standing sound waves. Standing waves are generated on the rod by holding it firmly at a nodal point in one hand then, with some rosin, stroking it firmly between the thumb and forefinger of your other hand. It may take a little practice at first, but once it is done properly and the rod is resonating it produces a very clear and audible tone.