[103] The gong, drum, bell, and cymbals all set up sound by concussion and these are called bombastic instruments.
By this I mean that what we call noise is sound set up by uneven air waves[104] in time and volume while music is made by a tone, or tones, of even air waves. Any musical instrument that produces sound by shock, or concussion as it is called, is said to be bombastic.
[104] For the theory of air waves and sound see The Magic of Science by the present author, published by Fleming H. Revell and Co., New York.
When a bombastic instrument is played alone the sounds set up by it are not very sweet or musical but if you will use a set of eight of them, or octave as it is called, and tune them so that the pitch—which is the number of air waves that are produced and heard in a second of time—of each one is a note higher than the one before it and then make first one and the other vibrate you will produce pleasing tones, and by combining these tones properly you will have a resemblance of what we call music.
The Musical Coins.
—How to Make Them.
—A simple and very pleasing way to show that there is music even in cold brass is to take a piece of sheet brass, or, better, sheet steel, about ¹⁄₁₆ inch thick and scribe on it with a pair of compasses eight circles whose diameters range from 2 inches to 3 inches.
Fig. 106a. the musical coin
Saw them out and file them down so that each one will ring out a whole number, as it is called in physics; that is, if the largest and deepest toned coin, or disk, makes 250 vibrations a second, the next one must make 500 vibrations a second, the next 750 and so on until the smallest and highest pitched coin will make 2000 vibrations a second.