excite pain, or to border upon it. It is agreeable to this, that discords become at last pleasant to the ears of those that are much conversant in music, and that the too frequent recurrency of concords cloys.
Sixthly, Concords sounded in succession seem to have the same effect, in kind, upon the ear, as when sounded together, only less in degree. But discords in succession do not offend, unless the chromatic succession of half notes, or some such remarkable ones, and even these please at last. All this follows easily from the last paragraph; and the present paragraph, with the two last, taken together, contain the principal grounds of the natural and original pleasures of music. The pleasures which it derives from association will be considered hereafter.
Sounds ought to decrease in the reciprocal duplicate ratio of the distance, did they not receive some support from the reflection of the bodies over which they pass. This makes them decrease in a less ratio; however, they do decrease in general with the distance; and this decrease, being an associate of the increase of distance, ought to suggest it to the imagination. And, agreeably to this, we may observe, that, when the wind opposes the sound of bells, they appear farther off; when a person calls through a speaking trumpet, he appears nearer, than at the true distance.
As to the position of the sounding body we have no clear or certain criterion, unless it be very near us; so as that the pulses may strike one ear, or one part of the head, considerably stronger than another. Hence we judge of the position of the speaker, or sounding body, by the eye, or by some other method independent on the ear. And thus, if from some mistaken presumption a voice, or sound, shall be deemed to come from a quarter different from the true place of it, we shall continue in that error from the strength of that mistaken presumption.
By laying these things together, and also considering farther, that indistinctness in articulate sounds is an associated mark of distance, we may see how ventriloqui, or persons that speak in their throats, without moving their lips, impose upon the audience. Their voice is faint and indistinct, and therefore appears to come from a more distant quarter than the speaker. The hearers look about therefore, and, being surprised, their imagination fixes strongly upon that corner, or cavity, which appears most plausible; and afterwards they continue to impose upon themselves by the strength of this prejudice.
