The acoustic guitar is capable of producing musical sound primarily as a result of the kinetic energy of it’s vibrating strings setting the soundboard (or top) in motion. The relationship between the soundboard and the back of the guitar can be understood as an interaction between two plates. If one were to liken the soundboard to a speaker cone in a cabinet, it would be necessary to set the back of the cabinet in motion to complete the analogy. Another way to describe the relationship of the two plates is to consider the workings of a bellows, with air moving between the soundboard and the back. Unlike a bellows, though, the plates of the acoustic guitar are rigidy held apart by the sides (ribs, rims) of the guitar. All three components (the soundboard, the back and the sides) together form the body of the guitar which is, in effect, a soundbox or chamber. The woods used to construct the body are often referred to as tonewoods.
Traditionally, acoustic guitar bodies have been built using softwoods (such as Spruce or Cedar) for the soundboards and hardwoods (such as Rosewood, Mahogany or Maple) for the backs and sides. Over the years, adventurous luthiers have explored the depths of wood resources and combinations. Today it is not unusual to see guitar bodies made using all hardwoods (such as Koa, Mahogany, or Myrtle) or even all softwoods (such as Douglas Fir).
This luthier believes that traits and characteristics of various species of wood are observable, if not recognizable. My own general understandings are presented below in order to offer a comparison between available species. This is, by no means, an exhaustive tonewoods database but, rather, I have included several of my favorite acoustic guitar construction woods, predominantly North American species (mostly found in the Pacific Northwest), for your reading and viewing pleasure.
By strict definition, only a few woods are capable of independently producing what we would generally consider to be musical tone. Those that can are often said to have a vitreous or glass-like quality where, when struck, the sound they generate is likened to the ringing of a bell or gong. One outstanding example of such a tonewood is Brazilian Rosewood, traditionally used to construct the marimba, a percussion instrument made up of wooden bars that are struck with a mallet. Metal pipes suspended below the bars amplify the resonant frequencies. The size of the piece of wood alone determines the pitch of the note. Wider, longer bars of Rosewood reproduce lower notes, while narrower, shorter bars are responsible for higher notes. See my article Wood is Wood...Until it is More for a video featuring the marimba. Not surprisingly, the most common woods used in guitar construction, the Rosewoods, Cedars, Spruces, Redwood, etc., also happen to be considered true tonewoods.
Another understanding of the term tonewood applies to any wood used in the construction of a guitar. The overall sound of a given instrument is generally acknowledged to be the sum of it’s parts. Curiously, unlike a wood that rings like a bell when struck, a wood that simply goes thud! or thunk! may be incorporated into an instrument that sounds surprisingly good when played. (NOTE: This understanding lends credence to the belief that the design and construction of the guitar may play an even more significant role in the resultant musicality of the finished instrument than does the particular selection of the wood(s). See my article Handcrafted vs Factory-built for more on this topic.)
The cellular structure of a given wood determines it’s distinctiveness, both visually and tonally. Much like wine produced from grapes, guitars built from various species of wood can have definable characteristics. Just as a fine Pinot Noir wine is recognizably different from a Cabernet Sauvignon regardless of how it is produced so, typically, is Brazilian Rosewood recognizably different from Claro Walnut, regardless of how the guitar is constructed. However, two vinters may produce two distinguishable wines using the very same grape by altering their harvesting or fermenting technique(s). In the same way, two luthiers can produce two distinct guitars using the same wood, but altering their build methods. Debating the degree to which the senses can be trained to identify subtle variations in wine or food, let alone wood, is not the objective of this article, nor does this luthier believe it necessary to score perfectly in some blind Tonewood Identification Listening Test ( B-TILT™ -LOL-) in order to appreciate one wood over another.
The characteristics associated with various wood species should not be confused with wood quality, nor should these characteristics be relied upon solely to determine the sonic potential of a given guitar. I believe that, in the right hands, measurable factors such as volume, mass, density, and modulus of elasticity (a given wood’s resistance to being deformed when force is applied) play the more significant roles in the overall tone and responsiveness of an acoustic guitar, and should be the determining factors when selecting wood. But that is a topic for another article.
Sitka Spruce is a softwood known for having a very high stiffness (or strength) to weight ratio, both across-the-grain and along-the-grain, making it a popular all-around choice for guitar soundboards. Capable of producing strong fundamentals with few overtones, Spruce is a good choice for players who demand a wide dynamic range. This tree is native to the Pacific coast of North America in forests ranging from Oregon to Alaska and has been measured having heights greater than 300 ft. Colors range from off-white to pale yellow and, while being straight grained, variations known as bear claw can be visually stunning. With so many guitars being made over the decades having soundboards of Sitka Spruce, this softwood has become something of a benchmark by which other tonewoods are compared.
Though soft enough to dent with a fingernail, WRC can match or exceed Spruce in it’s stiffness to weight ratio, though this stiffness is typically notable along the grain only. This may explain why WRC can be “overdriven” more readily than Spruce, and is sometimes avoided by more aggressive players. WRC is lighter than the Spruces, so a WRC soundboard can be left a bit thicker to compensate for it’s shortcomings in across-the-grain stiffness. Using our bell analogy, a low damping factor allows a WRC soundboard to ring a bit longer than many other soundboard tonewoods. Along with a winning combination of rapid note response and warm and lush overtones, it is easy to understand WRC’s reputation among fingerstylists as the tonewood to beat. The Western Redcedar is native to Oregon, Washington and British Columbia with smaller forests found in parts of Idaho, Montana and Alberta. It is a magnificent tree growing to heights of 200 ft. and often reaching ages of 1000 years or more. Reddish-brown to brown in color with straight grain, Western Redcedar is popular with fingerstyle players and those wanting a warmer overall sound.
The largest of the evergreens, the Redwood (or Sequoia - both terms are accurate) can attain heights of nearly 380 ft. and is native to southern Oregon extending as far south as central California. The tallest tree in the world, Sequoia sempervirens, and the largest tree in the world (by volume), Sequoiadendron giganteum, are both Redwoods, though the latter is sometimes referred to as Giant Sequoia. The reddish hue and distinctive fragrance of the lumber of this tree make it easily recognizable. Wood from felled, older trees is desirable for it’s increased cross-grain stiffness. Redwood is often described as sounding slightly more complex than Cedar, and is also a popular choice among fingerstyle players. Commonly straight grained, figured or flamed Redwood is quite beautiful in appearance. Redwood happens to be one of my personal favorites.
Heavier than Spruce, Cedar and Redwood, yet possessing one of the highest stiffness to weight ratios of all the softwoods, Douglas Fir is an often overlooked tonewood. This mighty tree, at 330 ft. is exceeded in height only by the Coast Redwood. Douglas Fir forests range from central British Columbia to central Mexico, extending eastward as far as west Texas. Color ranges from pale yellow to reddish-tan, and the grain is straight. While this wood is typically not as aesthetically pleasing as one of the Spruces, and is a bit heavier, it may rival any Spruce, tonewise, and is definitely worthy of consideration.
Lighter than Douglas Fir, yet as stiff if not occasionally stiffer, the highly aromatic Port Orford Cedar is actually a Cypress. Reaching heights of 200 ft., these trees can be found along the coast of southern Oregon and northern California. Tonally, Port Orford Cedar sits comfortably between Sitka Spruce and Western Redcedar. Paler in color that Western Redcedar, this relatively straight-grained tonewood can also sport curl, a particularly stunning variation. And did I mention that it smells great?
The leaves of the Bigleaf Maple can easily span 12", hence it’s name. These trees are found in the Pacific coastal region of North America, ranging from southern California to Alaska’s southern border. The largest of these trees resides in Oregon and measures 8 feet in diameter and 88 feet tall. Softer than Rock or Sugar Maple, Bigleaf is sometimes referred to as Quilted or Curly, Tiger, Flamed or Fiddleback Maple due to the prevalence of a couple of 3-D phenomena that can occur in the grain pattern. When present, flatsawing will reveal the quilted pattern, where quartersawing is necessary to reveal the curl (Curly, Tiger, Flamed, Fiddleback). Though these patterns can be seen in other species of Maple, Bigleaf Maple is known for having the highest grades available. Acoustic guitars constructed with backs and sides of Maple, all the potentially spectacular aesthetic qualities aside, are typically regarded as being bright and crisp sounding. This is likely due to the near tonal transparency of this hardwood.
5 foot diameter, 60 foot high Walnut trees are less common today in their native habitat of Oregon and California than they were 100 years ago due to the high demand for this lovely wood. Claro Walnut works easily and can be seen in everything from turned wooden bowls and carvings to rifle stocks and high-end furniture. A Walnut guitar is well known for having definition, producing very strong fundamentals with rapid note decay. This may be due to the wood having a relatively low sound velocity potential with more internal damping. One could say Walnut is more acoustically transparent than Rosewood, and may actually showcase the soundboard material better as a result. Often paired with Cedar (also known for it's warmth and articulation), Walnut is well suited for fingerstyle guitar and studio work. If a Rosewood-backed guitar would be chosen for an un-amplified outdoor campfire sing-along, a Walnut-backed guitar might be selected for the evening’s indoor intimate fireside performance.
With grain patterns ranging from straight to wavy to highly figured and colors going from sandy brown through orange-brown to olive, Oregon Myrtle is one of the most visually interesting tonewoods available. Found along the coastline from southern Oregon to central California, I consider Oregon Myrtle to be the versatile, all-weather radial tire of tonewoods, capable of producing both the low end response of Rosewood and the bright high end of Maple. Easy to bend (a delightful characteristic, especially when building Venetian cutaways) and seemingly hypo-allergenic (having no known adverse health affects), this wood is a pleasure to work with, always interesting to look at and a joy to listen to.
From the big island of Hawaii comes this unusual golden-brown hardwood, sometimes seen with streaks of reddish-brown or black and having straight, wavy, figured or even flamed grain patterns. Like Oregon Myrtle, Koa is easy to work and is not known to produce any adverse health conditions. Often compared tonally with Mahogany, a Koa guitar can provide a very clean and well-balanced sound. It is not unusual to see an all-Koa (back, sides and soundboard) instrument.
Stronger, denser and heavier than it’s close cousin Brazilian Rosewood, Cocobolo is a gorgeous wood, though it can be difficult to work with. Having relatively straight grain with colors ranging from yellow-orange to reddish-brown, this Central American Rosewood has a reputation for being both notoriously allergenic and cantankerous to glue. That said, it makes stunning looking guitars that sound fantastic! Pleasantly resonant with powerful fundamentals, a Cocobolo guitar is typically a head turner both visually and sonically.
Indian (also called East Indian) Rosewood grows in India, Sri Lanka and Indonesia. Known for deep, resonant bass response and a broad range of overtones, Indian Rosewood can range from golden brown in color to dark brown with purple hues. Straight grained Indian Rosewood is well regarded for being very easy to work and bend, and has become the standard in acoustic guitar back and sides, though figured wood is gaining in popularity. If we were comparing tonewoods to radial tires, Indian Rosewood would be my second choice for the all-weather model, suitable for most any occasion (see Oregon Myrtle).
Tone is such a subjective thing, and opinions regarding tonewoods may be as diverse as the number of people who share them. Much like the living trees from whence they come, those opinions are subject to change. There are few (some might argue there are no) hard and fast rules regarding the incorporation of wood(s) into an acoustic guitar. Let your senses be your guide. Did I miss describing a wood you may be interested in? Would you like to know more about a Cozad guitar?