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Many of the knowledgeable comments made already on the subject of cryogenics speak in terms of freezing a piece of metal. There is a little more to cryogenics and musical instruments than freezing a piece of non -ferrous metal. Please note my comme nts made here should be viewed as weighted, since I do offer the cryogenic freezing process in our repair facility. I will try to offer you without bias an overview of the cryogenic process and its relationship to musical instruments .

First I would like to mention that we are dealing with Non-ferrous metals (brass, copper, ambronze, nickel, silver, and gold) not steel. The purpose of using cryogenics to treat musical instruments is to help improve the resonance characteristics an d sound (end product). Musical instruments have many factors that effect sound and its production. They also have many obstacles that keep them from giving a musician all the fine characteristics of a good musical instrument.

Instruments cannot offer all of these characteristics due in part to thestresses created during the manufacturing process. Many individual parts are forced into their final shape. Instrument tubing and tone holes are drawn to size and bells are spun , while slide crooks, braces, and keyson woodwind instruments are stamped or hydraulically formed. The structure of the alloy metals brass, nickel, and copper is such that the atoms line up in perfect rows that are stacked densely on top of each other. The forming process pushes the atoms apart, causing internal friction. Often entire planes of atoms are dislocated; copper and zinc (brass) atoms once aligned in an organized manner become an entangled mixture.

The internal friction caused by dislocated or mis-located atoms effects-sound and/or resonance by impeding the instruments ability to resonate. Other factors such as impurity atoms that are not supposed to be present in the metal, can also effect reso nance characteristics. Since most metals used in the construction of musical instruments are some kind of alloy(brass, copper, and nickel), the possibility of contamination exists in the manufacturing process of these metals.

Problems compound with the assembly of parts which are fitted together then brazed and soldered. As molten braze and solder cools they draw the parts together even tighter. This is due not only to how well the parts are fitted, but also to the fact t hat dissimilar metals have contrasting rates of expansion and contraction. Some of us have had instruments resoldered that have been put together under tension or damaged in such a manner that creates tension between the braces and other parts. After resoldering, the instrument often responds better than before because we haveremoved the residual stress that results from misalignment of the parts.

Manufacturers have experimented with different techniques trying to build instruments without stressing the individual parts. Bell and slide crooks are annealed to facilitate bending and forming of crooks. This helpsreduce stress in the metal. Anne aling allows dislocations in the metal's atomic structure to resolve themselves. The atoms move around easily at annealing temperatures and this permits the grain structure to unite into large and larger grains. Annealing not only softens the metal, mak ing it more malleable, but also changes its resonance characteristics. These changes produce a darker sound due to the change in hardness and because the grain spacing is increased. The metal's ability to resonate diminishes so that only the strongest h armonics of each pitch are transmitted through the instrument.

The end result manufacturers and players search for is good tone quality. Much of this is due to the presence and intensity of the harmonics over the fundamental in each note. Anything you do to alter a horn, strip the lacquer, silver plate it, add we ight, dent it, and even cryogenically freeze it, effects the harmonic structure. Some changes are perceptible to the ear and some just to what the player feels.

With age comes wisdom?

They say "with age comes wisdom". In a way this holds true for musical instruments and their sound. Until now only older instruments (usually thirty-five years and older) have demonstrated that age itself can relievestress and improve the sound. Old Mt. Vernon and New York Bach trumpets as well as Kruspe and Geyer horns and the popular Selmer MVI series saxop hones are examples of instruments in this geriatric club.

Cryogenics

Cryogenics studies the properties of matter at temperatures lower than those that occur naturally. The warmest temperature dealt with by cryogenics is about -148F, the lowest is -459.67F (absolute zero). It is known that the properties of many materi als alter greatly at such low temperatures. These super low temperatures can stabilize many plastics and improve the clarity in optical crystal, while some metals and ceramic compounds,for example, lose all resistance to electrical current and become sup erconducting. Cryogenics has successfully been used to relieve the stress in castings and forged metals; even freezing cutting tools has resulted in increased wear characteristics.

Cryogenics is not new to the music industry. One brand of guitar stringshas been offering cryogenically processed strings for years. Also a manufacturer of professional flutes has been using this as a part of their manufacturing process as well as a well know Fr. horn maker.

Voo-doo magic?

Many years in the repair and technical side of music have allowed us to see a variety of wild ideas that claim to improve instruments. However cryogenic freezing is a true science that can improve the resonance quality of musical instruments.

Cryogenic will not turn a poorly made or designed instrument into a good one. But it can help improve resonance characteristics and make a good instrument just a little better.

By cryonically processing instruments, inherent stresses called "residualstresses" and "compressive stresses", are lessened. Sound quality improves because resonance character is not lost by dampening stress, and the dislocated position of the atom an d grain structure is relaxed so resonant energy is not diminished as much.

However the most important improvement in cryogenically frozen instrumentis in what is known as the grain to grain interface. Cryogenic freezing reduces the spaces between the grains so they have greater contact. This in turn makes the transfer of so und or resonance more efficient; less resonant energy is wasted.

The harmonic character or sound present before the process is enhanced. Cryogenic freezing does not change the character but generally increaseswhat already was there. Musicians find their instrument more efficient with a better core and more even timbre throughout. Dynamic levels and response are increased while the pitch center is more stable. Though intonation is not changed, many player's find it not only easier to lip notesup or down, but find the timbre of these notes more open.

Conclusion

Scientific evidence of this fairly new process on musical instruments isscarce at this time. It is very hard to be believe in something that one cannot see or touch, but after processing hundreds of instruments we have been able to collect valuable in formation on the benefits of cryogenics. Our experience with musical instruments and being able to perform the entire cryogenic process from start to finish has proven to us the positive effect on every instrument.

You asked: " On another subject, how do you find that heat treating your instruments compares to cryogenic freezing? I assume that the objectives are much the same, but how do the results differ?" There are two different objectives here. The purpose of heat treating the alloys is to soften them after they have become work hardened. This allows the metal to be worked further. Sometimes, it takes several anneals in order to form sharp bends, bell flares and some of the other components of a horn. But, it is also possible to alter the playing characteristics of the instrument by heat treating the bell flare. Many years ago manufacturers knew this and heat treated bells by using torches and observing the color of the metal as it was heated. The results of this process varied a great deal. Some horns were good and some not so, depending upon the skill of the maker. Fairly recently, heat treat furnaces came into use. They can be equipped with very accurate controllers so that the temperatures can be regulated within a few degrees. This allows manufacturers to control some of the playing characteristics of the instrument. It is possible to seperate out bells that have been heat treated as little as 40 degrees Centigrade apart. If the player or listener knows what to look for, a choice can be made between bell flares tempered to different hardnesses. These tests should be made using the same player and instrument body, with only the flare being changed. Of course, other components can be considered in the same way. With modern electronic equipment, what our ears hear becomes visible if the instrument is subjected to tests and driven electronically by a computer. This is a complicated subject and it is influenced by all of the other tapers, bores and alloys that make up a french horn.

Cryogenic freezing is a process whereby the stresses incorporated in an instrument during assembly are relieved. When a tube is joined either to a brace or another tube, it must necessarily be heated to nearly 400 degrees F. in order to melt the solder. As the joint cools the solder hardens at about 350 degrees but the metal keeps on cooling down to room temperature. The metal contracts and puts some stress on the assembly. Cryogenics is a process that cools the metal down to a very low temperature, below - 200 degrees F. At these low temperatures, the metal becomes closer to a liquid so that the stresses are relieved. However, the metal is restored to its' original condition when room temperature is reached. There are no scientific tests that I know of that have been performed to prove that the instrument is made better by being exposed to this process. It would be very expensive and require very sophisticated equipment in order to prove the claims made for this treatment. Players who have had this done to their instrument say they can feel an improvement. I don't disagree with this but there should be a way to check this out once and for all.

I hope this answers some of your questions.

Kindest regards,

Phase one: perform double-blind experiments and see whether the resulting statistics support the hypotheses that there is some measurable effect from freezing.

Phase two: (assuming a positive result from phase one) try to pin down the physical changes that cause the observed effects.

One consideration is designing reasonable playing/listening experiments that would yield quantifiable results. I wonder what the confidence limits might be; would it take four or fourty horns to gather enough samples to do good statistics?

This sounds like a project also for a hornists applied statistics student.