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 ose 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.

When each coin rings out its whole number, or nearly so, you will have what is known as a harmonic series. Now saw notches in the edges of each one as shown at A in Fig. 106 and then file them until the tone of each one is just right.

How to Play Them

To play a tune with the musical coins spin them on the top of a table - a marble top table is the best - and as each coin dies down 100 and its edge strikes progressively against the surface of the table it will ring out in a clear, loud tone.

Fig. 106b. How To Hold The Musical Coin To Spin It

The coins should be laid in a row on the table and

100 if you will look closely at the spinning coin you will see that when it spins fast at first the axis about which it rotates is its diameter and that the coin stands upright. As the coin commences to die down the axis about which it spins gradually begins to shift from the diameter to the center of the coin until finally at the finish the coin is spinning directly about its center. This motion is the same as the processional motion of the earth.

whatever note you want to ring out pick up the coin which will produce it, hold it as shown at B, and give it a little spin. You can soon learn to spin them with either hand and keep two or more of them going at the same time, when you will have that agreeable combination of tones that is known in music as harmony.

The musical coins are easy to learn to play and at a little distance off they look like real coins and are a very pleasing novelty.