Gong vibrations.

"The disorder, which is deliberately provoked into motion. Of harmony the result of a disharmonious state of being.
  Chaotic relationships that bear witness to a perfect marriage of tone and colour."

Poetic verse as a means of deliberation upon the behavior of a gong. Understanding and defining the gong is no easy task. Its chaotic underpinnings; the science and spirituality concerning of gongs. To the eyes of some, it would appear an easy task. To take into hand the metal alloy and hammer into creation a perfectly balanced ‘sonorous’ work of art.
Choice of which metal alloy varies with today’s gong makers. A Nickel alloy containing a high percentage of Copper, with the inclusion of Nickel is the preference of Paiste. Brass and Bronzes of varying tempers and purities are preferred by UFIP. Steel is used by Matt Nolan, Steve Hubback and Kimerism Gongs. The Gong makers of the Indonesian islands, working as they have for hundreds, if not thousands of years work with smelted raw and scrap materials. The bronzes they smelt are not as pure, yet still in possession of wonderful tones.
Fundamentally each alloy sings its own song of harmony, all of which are already suited to the manufacture of percussion instruments. With the knowledgeable use of the hammer, each blank is crafted into an expressive medium of harmony.

It is through the deformation of the metal alloy, that the gong maker is able to nurture timbre. With precise administration of hammers, of varying weight, and force. Angular differences, flexural displacement and stresses all configure towards, and contribute to the ‘modes of vibration’. Our interaction with the gong, by striking with a mallet upon the surface initiates the fundamental frequency. Which in turn ‘excites’ other immediate ‘localised’ modes of vibration if such have been imbued into the gong. Most usually, there is a transposition from lower frequency modes to those of higher frequencies.
Gong design varies and so it is possible to determine the transposition of frequencies. Flat, dished and folded rim gongs all convey individual character and variations in pitch glide is possible.
 
Through experimentation and with an understanding of the capabilities of metal alloys. Then only we can develop the practice of gong making. Those knowledgeable minds, implementing angular differences, and utilising the elasticity of the metal alloy. Variations of thickness and radius, the uniformity of thickness.
All these and other important elements are taken into account and held in the mind of the gongmaker.
It is a process, moreso a ritual honored over a period of time, months infact for the larger gongs.

Tension is introduced into the metal alloy by skilled hands, further tension will manifests as the individual begins his or her period of interaction. These tensions are carried transversely throughout the gong, exciting other modes of vibration.
If we were to take the example of an ordinary styled ‘orchestral’ gong, we might discover the following behavior. The fundamental frequency mode activated through the striking of with a mallet. Exciting and fuelling further modes of vibration which would then be of integer multiple frequencies of the fundamental frequency. Having been subjected to no hammering, the modes of vibration vibrate in unison and amplitudes are constant. A phenomenon known as mode locking occurs, and it is possible to tune a gong to a precise frequency.

In comparison we should study the behavior of another variation of gong. In possession of multiple hammerings, and a greater number of modes of vibration. Even if there is little or no angular stressing. Such a gong may be thought upon as having a nonlinear character, it's output is not in proportion to the input. Hammering introduces the nonlinear behavior; resistances are created which interrupts the symmetry.
The ‘Sound Creation’ series of gongs by Paiste could be thought upon as we begin to identify such a gong. The culmination of multiple ‘faster decaying’ high frequency modes of vibration, coupled together in chaotic form and response giving the Sound Creation Earth gong its unique character. Standing waves contribute to the behaviour, and response. To the ear of the individual who interacts with the gong there is harmony, on a subtle level they may discern some of the chaotic response.
Cladni plates illustrate the vibrational diversity that is attainable. When frequency is applied to a sheet of suited metal alloy covered in sand, uniform patterns appear. This phenomena is referred to as 'Cymatics'. These patterns change, and evolve further with changes in frequency applied. This is a technique which can be utilised as well as the use of electronic tuning equipment in the art of gong making.
Referred to by the Gongmaker to ensure balance of tonal structure, and that the frequency response of the gong is correct.

Maybe it would be true to suggest that the importance to acquiring the required character of a gong lies not totally in the metal alloy.
Ultimately it is within the hands of the Gong maker, and his or her skill with the hammer that the greatest quality is inherent.