Turning designs into great instruments isn’t easy. Technical drawings can’t convey the intended tone of an instrument, or the construction methodology required to create the desired characteristics and sound. Before building a new guitar can begin, the plans and intentions of the designers are discussed with the craftspeople at the factory in order to develop an appropriate production process. Every guitar is different, and coming up with the ideal production methodology and workflow for each guitar is critical.
Sometimes “overdoing” things is the only way to ensure that the desired quality is achieved consistently and in every possible situation. Yamaha takes manufacturing details to extremes in many cases, but the final results are worth it. The Yamaha process of pre-matching acoustic guitar bodies and necks before finishing, where the neck and body are matched up early in the crafting process, is one example. Experience has shown that the quality of the neck-body joint plays an important role in maximizing the instrument’s tone and response; in short, the fit must be perfect with intimate contact between neck and body. The level of control and consistency that comes from building and finishing the neck and body as a matched pair is worth the extra effort.
There are some tasks that are best left to machines, particularly those that require extreme precision and repeatability; for example, cutting the fret slots in fingerboards is a critical job that is handled by precision computer-controlled machinery. But in order to deliver instruments that really meet guitarist’s needs there are elements that require individual attention and flexibility. That’s where the skill and experience of Yamaha craftspeople really shines.
Yamaha works hard to ensure that every guitar and bass leaves the factory in optimum playing condition. Some players may want to make minor adjustments to match their individual playing style, but important details such as fret levelling and finishing are taken to custom-shop level right at the factory. Final assembly is a production step that requires the utmost care if optimum tone and performance are to be achieved. Parts that are not properly aligned or not solidly attached can degrade both sound and playability, so assembly workstations and processes are designed and set up for smooth, efficient assembly so the builder can concentrate fully on achieving perfect results.
Most of the tools used for making guitars have to be made by hand for the purpose, and many are created specifically for a single model and won’t be used for anything else. Developing tools and jigs that make it easy for guitar builders to consistently produce perfect instruments is an important element of Yamaha’s approach to craftsmanship, but tools and jigs can wear and go out of alignment with use, so special care is taken to keep them maintained and in perfect working condition at all times: it’s a hidden but vital part of overall quality control.
Because of the reliance on skilled craftsmanship in the making of fine guitars, the only way to ensure consistent, continued quality into the future is to pass the know-how on to the next generation of craftspeople. This kind of skill can only be fully passed on person to person, through hands-on apprenticeship, so Yamaha makes this an official part of the guitar manufacturing process. The team of guitar builders changes with time, but Yamaha is dedicated to ensuring that the basic skills, as well as the many innovations developed along the way, are effectively passed on so that Yamaha guitars can continue to evolve.
The materials used to craft a guitar are chosen to match the role and characteristics of each part of the instrument. On an acoustic guitar, the top plays the most important part in transforming the vibrations of the strings into sound, and is usually made of a light, resonant wood such as spruce. Conversely, the sides and back of the guitar must be made from a comparatively stiff, heavy wood such as rosewood, in order to provide support for the vibrations of the top.
The process of balancing strength, sound and looks is repeated for every part of every guitar, and the best materials are chosen accordingly.
The drying process is a crucial stage in the making of Yamaha guitars.
When building a guitar, ensuring the wood used has the right level of moisture, and that the moisture level is stable, is essential to the quality of the finished instrument. Yamaha produces a great many instruments that are made of wood, and as a result, has accrued a wealth of knowledge on how to lower the amount of moisture in an instrument, and then maintain the desired moisture level.
Yamaha utilizes a combination of natural and artificial drying to reduce the moisture to a level of approximately five percent. Wood that has finished artificial drying is seasoned in a room at constant humidity and temperature to ensure that its moisture content remains stable in the wide variety of conditions it may encounter around the world.
A.R.E. is a proprietary technology developed by Yamaha that alters wood in the same manner as years of aging does, breaking down and changing its internal structure.
By changing the shape of the wood fibres at a microscopic level and breaking down hemicellulose, a material that causes the fibres to stick together, ARE gives a guitar the same mature, rich, warm, open sound as that of an instrument that has been played for years. A.R.E. is applied as part of the final drying process.
Advanced techniques utilizing computer-controlled machinery are used for processes that require high precision and repeatability, such as cutting fret slots and machining guitar bridges. These modern guitar building methods are used at Yamaha factories in Japan, China, and Indonesia, and combined with the traditional handcrafting skills and know-how developed through more than 60 years of crafting guitars in Japan and at our factories around the world.
The bracing on an acoustic guitar is an extremely important element in maintaining the strength of an acoustic guitar’s top while transmitting the vibrations of the body throughout the instrument.
At Yamaha, we utilize methods including vacuums and air-presses to ensure a high level of secure clamping for the bracing. These methods preserve the strength of the bond between the bracing and the guitar top and back, reducing the loss of vibrations throughout the instrument.
Carving the bracing requires extreme skill and sensitivity from an experienced guitar builder. Chisels are used to shape the bracing, and then the craftsman taps it to check its sound. This task is repeated with painstaking care to produce the perfect bracing shape.
Acoustic guitar linings are thin sheets applied to the inner surfaces of the instrument sides so that they can be joined to the guitar top and back. They play a key role in transmitting the vibrations of the guitar top from the sides to the back, spreading them throughout the body of the instrument. As with every other step in building a guitar, precision is key – the linings have to be perfectly shaped, and uniformly and firmly fitted to the curves of the guitar body in order to be strong and stable.
To make the curved shape of an acoustic guitar from a flat piece of wood, heat is applied to the side, which is then curved using a press. After removing it from the press it is placed in a mold, and cooled, eliminating moisture. This process has to be monitored carefully as applying too much heat will cause moisture retention, causing the guitar to deform later, while too little heat can result in the sides cracking.
Different Yamaha guitars use different processes, but for L Series acoustic guitars the top and sides are glued first, followed by the back.
This step-by-step process results in less residual stress when the body is complete than when they are glued at the same time, making it easy for the whole body to vibrate and product a rich, resonant tone.
There are two main types of binding —those made from resin, and those crafted from wood. When gluing resin inlays a special glue that melts the resin while gluing is used and then clamped to accelerate adhesion. For wood inlays a different adhesive is used, with parts being fixed firmly in place with clamps during the time it takes for the bond to dry.
Yamaha’s custom-built classical guitars are made using a Spanish-style construction in which the heel of the neck and the neck block are crafted as a unified whole from a single piece of wood. For all other models, the neck is inserted into a groove cut into the body, forming a dovetail joint.
A single stroke with a plane may change the strength or angle of the joint, affecting the sound or action height of the guitar significantly, so this method requires a high degree of precision and skill.
Guitar finishing work is separated into four main processes: the undercoat and mid coat for the wood filler, top coat, and polishing. Sanding is carried out at each stage, moving gradually to a finer-grained sandpaper as the surface becomes smoother.
During coating, a film approximately 10 microns (0.01mm) thick is applied precisely with each spraying. Each coating is applied in a layer that is not too thin, nor too thick, to avoid beading of the paint. The finishes used are developed in a joint effort between Yamaha’s in-house research divisions and finish manufacturers, with an emphasis on sound, ease of application, and the ability to cope with changes in the guitar’s environment.
Shellac is used in coatings for custom classical guitars.
This is a traditional method of coating used in Spain, which contains the purified secretions of the lac bug, an insect found in Southeast Asia. Shellac coating is the process of dissolving this secretion in alcohol and then applying it in thin layers with a pad. Each coat is approximately 1/100th of the thickness of a normal coat of paint.
Shellac coatings are applied in approximately 300 layers, and must be dried after each layer. Because of this, a shellac coating takes around three months to complete.
Buffing is the last process in applying the guitar’s finish..
A range of different abrasive compounds and buffing cloths are used to buff the guitar to a brilliant shine. Different finish types result in coatings of differing hardness, so it is necessary to take measures such as altering the RPM of the buffing machine or reduce the strength with which it is applied to get a perfect finish.
After finishing, the surface of the fret board is sanded and the frets are installed.
The frets are fitted last because the shape of the neck changes after finishing and during the post-finishing drying process, so installing the frets prior to finishing would necessitate a great deal of sanding during the final adjustment of the guitar.
For electric guitars and basses with bolt-on necks, the neck and body are finished separately, and then joined at the start of the assembly process. Fitting them together without any gap and adjusting the angle of the joint to achieve optimum playability requires skill, precision and patience
After installing the frets on an acoustic guitar, the next step is to attach the bridge.
The bridge is clamped firmly to the guitar’s top to ensure that the string vibrations are transmitted properly.
Because attaching the bridge in the perfect position is crucial to an acoustic guitar’s sound and playability, a special tool is used to keep clamping strength at a fixed level and ensure that there is no movement or variation.
Final assembly is when the rest of the guitar’s hardware and parts, including any pickups or electronics on an electric guitar or bass are fitted. Every single part is adjusted carefully on each instrument to optimize the sound, ensuring that string vibrations are transmitted properly and playability is perfect.
After assembly and adjustment, some electric guitars feature a process called Initial Response Acceleration where the completed guitar is vibrated at specific frequencies and intensities . Subjecting the guitar to these vibrations eliminates stresses between parts built up during assembly, resulting in an instrument with excellent resonance, despite being completely new.
Inspection is carried out at every stage of the building process, but a final inspection is performed to double-check the sound and playability of each guitar.
If these are all approved and the guitar meets our exacting specifications, the exterior of the instrument is carefully inspected for marks and flaws. When that final hurdle is passed, the finished guitar is packed and shipped to its new home.
RESEARCH AND DEVELOPMENT
ACOUSTIC GUITAR ANATOMY
ELECTRIC GUITAR ANATOMY