How Guzheng are Made
Guzheng are assembled from shaped pieces of wood that have been cut, dried, and heat-treated to enhance their visual and acoustic beauty. 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. This enables the guzheng makers to balance sound quality, looks, and overall expense at different levels for different musicians.
Some instrument makers like Mitsuya Koto hollow out a log to create the guzheng, frame and all. That is a work-intensive process so they produce only high-end instruments from traditionally-aged wood. They have an excellent photo overview and video showing some of the steps:
By contrast, here is a video of the more common, assembly-by-parts method. Some of the methods are cheap and fast and don’t lead to the best sound - but put that aside and this video provides a great visual way to see the process for yourself. Read on for more details.
Guzheng Construction Process (Chinese). Video taken from Chinese River Band/River Arts Incorporated of Australia youtube channel. This video has been posted by multiple accounts over several years; Original producer is unclear.
Approximate dimensions of one Dunhuang-style S-Bridge 21-string guzheng are:
Length 164.5cm (64 3/4 in.)
Width 32.4 cm (12 3/4 in.)
Height 24.1 cm (9.5 in. including bridges)
Instruments vary by model and maker. Instrument makers change the dimensions to balance the overall size of the instrument, the tensions this will require for the strings, the volume of the resonance chamber, and the thickness of the soundboard itself.
Most guzheng soundboards are made from quartersawn planks of Paulownia. Read more about Paulownia and other options on the Woods page. 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 at Hardwood Distributors.org.
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 referring to the 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.
String Posts and Tuning Pins
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 the 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. They 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 roughly triangular with two feet on the soundboard and the tip supporting the string.
The modern bridge is typically constructed from one piece of wood with a string rest inserted at its tip. The insert material is typically bone, resin, or a combination of both. Some inserts were once made of ivory. Buffalo bone, plastic, and imitation ivory as the most common materials used in modern bridges. Imitation ivory is probably bone powder mixed with a resin.
The insert is notched to provide a resting place for the string. The hard material helps to transmit sound from the strings while protecting the wood. Without an insert the string would wear its way into the bridge, making key changes difficult and possibly requiring bridges to be replaced 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.
The Dunhuang company offers this height guidance:
Bridge #’s | Height, mm
1-3 | 49mm
4-6 | 51mm
7-9 | 53mm
10-12 | 55mm
13-15 | 57mm
16-18 | 59mm
19-21 | 61mm
Interesting work is being done in China on the development of hollow ceramic bridges. The denser ceramic transmits and emphasizes different aspects of the strings’ vibrations and thus sound. 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!