A Philosophical Essay of Musick

isochronous original: "isochronous"; meaning occurring at the same time or having a uniform period, and produce one single sound; as if the parts that vibrate separately are half parts, seconds, or thirds of the string: and how this may be caused, I will inquire.

If a string pendulum A weight suspended from a long cord is very long, and the weight at the bottom is not sufficient to cause the whole string to cut through the air; at first the pendulum will be held back by the resistance of the air, and afterwards it will put the whole string into motion. However, this motion will not be in a straight line, for the pendulum will return before the direct motion is completed at the top.

This will cause a clashing of motions. Being balanced between the force at the bottom and the restraint at the top, the crossing point will settle in such a division of the string that the motions will continue uniformly until the force is spent.

I imagine that if a musical string is struck in such a way that the whole string is not moved out of its place to cause the greatest vibration in the middle, there must be a crossing of vibrations. This is because before the motion is communicated to the farther end, the part of the string that was struck may have already returned to its original position. This crossing of vibrations, if the string is well-made, will occur at equal intervals and produce an octave, a fifth, or some other chord In this context, "chord" refers to a harmonic interval or a consonant note.

It is a common experience that a large string struck near the bridge with a bow—where the rosin takes only a small grip—will whistle and break into higher harmonies. Yet, if that same string were struck by the thumb, which moves the entire string out of its place, it would give the true tone The fundamental frequency.

The trumpet marine original: "Trumpet marine"; a tall, triangular-shaped string instrument used in the medieval and Renaissance periods that produces trumpet-like sounds using harmonics, which sounds entirely based on such breaks in vibration, is a large and long monochord A single-stringed instrument played with a bow near the end, which causes the string to break into shrill notes. Moving the thumb that presses upon the string provides the measurement for these breaks and, consequently, directs the specific tone to be produced. The jarring at the bridge follows the same measurement and makes the sound loud, in imitation of a trumpet, which otherwise would sound like a whistle or pipe.