Text: A Combination Tone is a third sound, which may be heard or measured, when two tones of different pitch are simultaneously sounded, and which are not heard, when either of these two tones is sounded alone. The two tones which give rise to a Combination Tone are termed its generators. There are two kinds of Combination Tones: Summation Tone: the vibration number which is the sum of these generator vibration numbers. Differential Tone: the vibration number which is the difference of the vibration numbers of its generators. Differential Tones may be of various orders: A Differential of the 1st order is that tone produced by two independent tones or generators. A Differential of the 2nd order is that tone produced by the Differential of the 1st order, and either of the generators. A Differential of the 3rd order is that tone produced by the Diffferential of the 2nd order, and either of the previous tones being either the Differential of the 1st or 2nd orders and/or one of the generators. A Differential of the 4th order is that tone produced by the Differential of the 3rd order and either of the previous tones; and so on. See Calculating Compound Difference Tones (next card) See Compound Difference Tones

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