How It’s Made
Guzheng are assembled from shaped pieces of wood that have been cut, dried, and heat-treated to enhance their visual and acoustic beauty.
There are two tracks of construction. The method of highest regard is the carving and hollowing of an entire log into the body of the instrument. Mitsuya Koto of Japan makes guzheng (and koto) in this style. They have an excellent photo overview and video showing some of the steps:
The more common method is to assemble guzheng out of separate soundboard, backboard, and frame pieces.
There are a host of ways the soundboard and backboard are shaped and another variety of design alternatives that individual instrument makers choose, but the general approaches are very similar.
Here is a video of a generic guzheng construction process. Some of the methods they use are mass-market, simplified processes that can have negative effects on the final sound or lifespan of the instrument. Put that aside and this video provides a great visual way to see the process for yourself. Read on for the details.
Approximate dimensions of one Dunhuang-style S-Bridge 21-string guzheng. Conversions are not exact and instruments vary by model and maker. That said:
Length 164.5cm (64 3/4 in.)
Width 32.4 cm (12 3/4 in.)
Height 24.1 cm (9.5 in. including bridges)
Some of the details instrument makers consider include the overall size and different tensions needed for the strings, the volume of the internal resonance chamber, and the thickness of the soundboard itself. Here's how they do it.
Construction of a Modern 21-String Guzheng
Modern guzheng are made in pieces. Typically the soundboard and backboard are shaped from various woods, the frame of the instrument is built in steps, and then the overall instrument is assembled. One advantage of producing the instrument from separate pieces of wood is that it is easier to mass produce this way and enables the instrument makers to balance sound quality, looks, and overall expense at different levels for different musicians.
Some instrument makers like Mitsuya will hollow out a log to create the guzheng, frame and all. That is a work intensive process so they produce only the high-end instruments. From this point on I'll talk only about the more common assembled guzheng.
Most guzheng soundboards are made from quartersawn planks of Paulownia. To quartersaw a log is to cut the log into planks as in this diagram. The log is marked or cut into quarters, then the quarters are cut at 45 degree angles to the center. This maximize the amount of plank with grain patterns that are as close to straight as possible. Straight grains mean the wood is stronger and generally has more desirable characteristics.
As the planks get smaller the angle between the centerline of the board and the curve of the grain or growth ring gets farther away from perpendicular, which is farther away from that nice, straight grain. Those smaller planks can be spliced together to form a full board, but the sound they produce will be a little different. There are other ways to cut planks so that each is a large size and has nearly straight grains such as rift cutting, but that wastes a lot of wood. You can see a diagram here.
The wood is then dried, a process also called seasoning in English. There are a few ways to do it, it's fascinating stuff! Head over to the Wood Drying page to learn more about those details. In brief: wood shrinks as it dries and will crack if it shrinks after it's part of an instrument. To prevent that cracking wood is dried and shrunk first and then turned into an instrument. There are different ways to do it but the end goal is the same: to get wood that is a stable size, sounds good, and will continue to sound good for years to come.
Once you have one such plank you have to shape it. Each plank is curved in two directions: Horizontally, along the width of the plank, and vertically, along the length of the plank. Cheng 1991 says curved soundboards used to be carved out of large blocks of wood. This provided exceptional sound but wasted wood. Nowadays boards are cut to a desired thickness, soaked, and then pressed into the desired curvature. A heat treatment step locks that curve into place. Cheng quotes the following numbers: Final board thicknesses are around 9mm. The horizontal radius of curvature ranges from 36cm to 45cm. The vertical or longitudinal radius of curvature ranges from 450cm to 860cm.
Those radii of curvature may seem crazy, but plugging them in you get a reasonable board:
It's important to remember that the soundboard is the center of the instrument. The head, tail, and frame add additional width, height, and length.
The dimensions of each soundboard depend on a number of things. Thickness varies based on the density of the wood used. Denser woods can be cut thinner than 9mm. Less dense woods are cut thicker. And as if all that wasn't enough, the soundboard in the top quality instruments is tapered, leaving it thicker underneath the bass strings and thinner underneath the treble strings. Carol Chang mentions a change in thickness of about +/- 1mm from the average - so a soundboard with a thickness of 9mm in the midrange might have a thickness of 8mm under the treble and 10mm under the bass.
The radii of curvature balance a few considerations. Curving the soundboard sets one boundary on the size of the resonance chamber inside the instrument, and I believe enhances the sound produced. Making the radii too small and thus the curves more severe can cause filaments of wood to separate from each other. Those filaments will then vibrate separately from the rest of the instrument decreasing the quality of the sound.
Some instrument makers carve sound grooves into the underside of the soundboard. They do this either by hand or through a mechanized process. Mitsuya Koto carves them by hand. I don't have too many sources on the consequences of sound grooves but I've heard it mentioned it makes the instrument louder. If you know of reasons, please, send them in!
For more information about other considerations of soundboards see Carol Chang's discussion at Chinesezither.net.
The Soundboard is the curved board on the front. The Backboard is the board in the back. Older zhengs and zithers had flat backboards. During the instrument reforms of the 1950s the instrument makers found it necessary to curve backboards convex up, approximating the curve of the soundboard. They do this to limit the size of the resonance cavity. That big open space in the center of the guzheng helps amplify the sound of the plucked strings while adjusting the overall quality and characteristics of the sounds the instrument produces. As one reference relates: "The approximate resonant pitch of the air chamber is important to the sound, determining as it does which frequency ranges will be enriched. That resonance is jointly determined... by the volume of the chamber and the size of the [sound holes]." ("Musical Instrument Design: Practical Information for Instrument Making" by Bart Hopkin, 1996).
Aside from being curved, the backboard is the place where the sound holes are carved. These are needed for the amplified sound of the strings to escape and reach the audience. The shape or total surface area of the sound holes affect the pitch range the chamber resonates with and how it does so. I don't have many sources on instruments with resonance chambers or sound holes as large as the guzheng. Placement, shape, size, and total surface area of the combined holes could have different effects. Then again, perhaps after a certain point size doesn't matter. All I can say is that zhengs have had different sizes, shapes, and placements of sound holes throughout history and continue to do so today.
Inside of guzheng there are often supporting braces that sit between the soundboard, sides, and backboard. They act like the sound posts found in violins, supporting the soundboard and passing vibrations throughout the instrument. Designs vary; guzheng carved out of a single piece of Paulownia might not have them at all. The common assembled guzheng typically do.
I'm still looking for sources on the trade-offs and purposes of these different designs. If you know, send me a message!
The frames of guzheng are everything that's not the sound board or backboard. When an instrument maker advertises Sandalwood, Rosewood, or other exotic materials, they are refering tot he wood used in the frame. The choice of materials do contribute to the qualities of the sound the instrument produces, but not as much as the quality and wood choice of the soundboard. Head over to the Woods page to learn more about that.
I have found the least information in English about the frame, so please, if you know more, send me a message through the form below and help me add this information! What I do know is that the frame provides the overall structure of the instrument, gives it strength, and contributes to the overall dimensions of the resonance cavity in its interior.
From an art perspective, it also provides a massive canvas for all manner of artistry to be displayed.
Strings posts used to be exposed; see photograph at right of a guzheng made in that style. This design is centuries old, though this particular guzheng is made in the 1980s.
The pegs were turned by a detachable handle, which at one point was ornamented to look like a massive gate key. Nowadays modern guzheng use a right-angle tuning wrench to tighten and loosen the tuning pins. The modern wrench looks nearly identical to those used on western instruments such as harps- but traces of the old way still remain. The name of that wrench, 筝匙 (zhēng shi) , translates as "zheng key".
There are advantages to changing the tuning mechanism to pins inside of a compartment. Chief among them is right-angle curve around the fixed bridge. That provides a mechanical assist that reduces the likelihood a tuning pin will loosen from play or temperature changes. Once an instrument's strings are settled in, the tuning pins can stay untouched in their compartment for hours upon hours of play, leaving tuning adjustments to the movable bridges. Exposed tuning pegs like those pictured are held in by friction, meaning any expansion of the surrounding wood can lead to the pegs rapidly unwinding.
Bridges are crucial to the guzheng. The allow for fine tuning and transmit the vibrations of the strings to the soundboard and resonance chamber inside the instrument. Bridge shapes are many and varied. The most common I have seen are in a roughly "V" shape with two feet on the soundboard and the tip supporting the string.
The modern bridge is typically constructed from one piece of wood with an insert placed in the top point to act as a string rest. The insert material is typically bone or ivory. Through the years the insert has also been made of plastics, resins, and ground bone or ivory mixed with resin. I could not offer guidance on how to identify what material sits at the top of a bridge, though Carol Chang lists buffalo bone, plastic, and either a real or imitation ivory as the most common materials used in modern bridges. With the world's sensible move against elephant ivory usage, I'd bet inserts today are either solid pieces of bone or bone powder mixed with a resin.
The insert is notched to provide a resting place for the string. The notch is smoothed, providing a resting place for the string while protecting the wood of the bridge. Without an insert the string would wear its way down, through the bridge, meaning bridges would need to be replaced multiple times over the life of the instrument.
Bridges typically display a vertical grain when viewed from the side. When viewed from the top, they show a horizontal grain pattern though there is some variance.
Interesting work is being done in China on the development of hollow ceramic bridges. The denser ceramic transmits and emphasizes different aspects of the sound than wood. Indeed, bridge makers have for centuries used different densities of woods and different sizes of string rests to strike a balanced sound transmission. Other aspects of the bridge to consider are the overall height, thickness of the legs, and the curvature of the notch cut in the string rest.
And there you have it!
A brief overview of some of the considerations that go into guzheng making. If you have feedback or more details and sources to share, please email me!