Newton's Tune Analyzer
   This unique piece of apparatus uses Lissajous figures to show that the ratio of the frequency ratios in a diatonic scale are ratios of small numbers. On the right-hand side is an air-driven vibrating reed (a harmonica reed) with a small mirror attached to its free end. The octagonal, revolving drum contains eight reeds, ranging up the scale from the same frequency as the fixed reed to its octave. 

   In use, the box holding the fixed reed would be rotated
90 degrees, making it oscillate at right angles to the other reeds. A beam of light reflecting from the two reeds in succession undergoes simple harmonic motion in two perpendicular directions, thus producing a Lissajous figure when the beam strikes a screen. The shape of the figures produced by two frequencies which bear small number ratios to each other is well-known.

   The apparatus is made by Newton and Company of London, and dates from the last quarter of the nineteenth century. It is in the collection of the National Museum of American History of the Smithsonian Institution.

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