The top or soundboard of a guitar must absorb the vibrations generated by the strings. The top needs to be soft and flexible.
The back and sides of a guitar must reflect the frequencies generated by the top; therefore, the back and sides are constructed of wood that is harder and more dense than the top. The wood of the back and sides also “colors” the sound depending on its type.
The most traditional and preferred wood choices for the back and sides of acoustic guitars are:
Rosewood (genus , Dalbergia ), Mahogany ( Meliaceae ) and Maple ( Acer );
In addition, Cypress , Yellow Cedar and Sycamore are used for Flamenco Guitars.
Finally, the preferred woods for solid-body electric guitars are Ash, Alder and Mahogany.
There are a number of other woods used for the back and sides of acoustic guitars which are either more rare or exotic and/or less preferable. Some of these are:
Bubinga ( Guibourtia , often called African Rosewood though it is not of the same species as rosewood) and its close relative Ovangkol ( G. ehie ), Koa ( Acacia Koa ) and its close relative Australian Blackwood (Acacia Melanoxylon ) or Black Acacia, , Striped or Macassar Ebony ( Diospyros celebica ), Imbuia ( Phoebe Perosa ), Lacewood ( Roupala Brasiliensis) , Oregon Myrtle ( Umbellularia Californica ), also known as California or Bay Laurel or Pepperwood, Padauk or Purpleheart (Pterocarpus soyauxii) , Palo Escrito , Pau Ferro ( Machaerium Villosum ), Pau Rosa ( Swartzia fistuloides) , Walnut ( Juglans California ), Wenge ( Millettia laurentii ), Zebra Wood ( Microberlina Brazzavillensis ), and Ziricote ( Cordia dodecandra ).
For complete descriptions of these tone woods for use in guitar lutherie, check out wood sources such as Luthiers Mercantile, www.lmii.com or Colonial Tonewoods, www.colonialtonewoods.com , or the many other listings on the internet.
Rosewood imparts dark, rich, chocolate tones to the sound of a guitar. It is so very popular a choice, both for its acoustic properties as well as its beautiful appearance, that many varieties, such as Brazilian and African Blackwood ( D.melanoxylon ), have been very depleted and are quality pieces are hard to come by. There are several other varieties of rosewood used in guitar making:
Amazon ( D. spruceana ), Cocobolo ( D.returna ), East Indian/Palisander ( D. latifolia ), Honduran (D. Stevensonii ) and Madagascar (D. Baroni).
In addition, there are some exotic woods which have similar appearance, density and acoustic properties to rosewood. These woods will be increasingly used as true rosewood becomes more rare:
Pau Ferro or Morado , Palo Escrito , Wenge , Zebra Wood and Ziricote
Mahogany is another very popular choice for guitar backs and sides. It, too, is becoming more difficult to obtain in good grades. Mahogany is less dense than rosewood, and its tonal properties are more bright and penetrating. Originally obtained from Honduras ( Swietenia Macrophylla) , it is now most often obtained from Brazil . Other varieties such as African ( Khaya ) and Sapele, which has more prominent vertical stripes, are very close to Honduran in appearance and tonal properties.
Mahogany, like rosewood, has wide appeal and can be used with success on a wide range of body sizes and guitar types.
Mahogany is occasionally used for top wood as well, although it is seldom a preferred top wood, being stiffer than spruce or cedar.
The third most popular back and sides choice for guitars is Maple ( Acer pseudoplatanus ). Maple has long been used for other stringed instruments, as well as guitars. It is lighter than rosewood, often lighter in weight than mahogany; and in acoustic steel-string and classical instruments it provides the brightest, most sparkling tone. It is also quite beautiful in appearance, in some cases having great depth in its flames and curl. It is the overwhelming first choice for archtop guitars, and it seems especially effective in large body guitars like jumbos. Perhaps maple helps to maintain clarity when the bass is so enhanced by a large acoustic cavity. Even so, maple is widely used in all body sizes and shapes. It is also often used as a top veneer on electric guitars.
Koa is an exotic wood grown only in Hawaii , which has been often used in guitar construction. Its dramatic patterns and color have made it very desirable in guitar backs and sides. It is also occasionally seen as top wood, although it produces a harder, less desirable tone when used for a guitar top. Koa is almost an endangered species these days, and highly figured Koa is hard to obtain. Many guitar makers are experimenting with Hawaiian Koa's close cousin, also an Acacia, Australian Blackwood.
Koa produces a brighter sound than rosewood but with darker overtones than mahogany. It is an excellent choice for many guitar sizes and types of guitars, although almost never seen on classical guitars
Walnut is increasingly used for guitar backs and sides, especially as other choice woods become less available. Walnut has a brownish-grey color and works well for backs and sides. It is used for acoustics and classicals alike. Walnut is not quite as rich in its tonal palette as rosewood, but it is less bright than Mahogany
Cypress is the preferred choice for the backs and sides of Flamenco guitars. It is a light wood, and according to our sources, chosen originally because other woods were not available to the early builders of flamenco guitars. Whether or not this story is apocryphal, the sharp, percussive qualities of these early instruments became identified with flamenco music. Flamenco musicians prefer a light instrument which projects well enough to be heard through the singing, clapping, and foot stomping of Flamenco music. Cypress , being extremely light but strong, is the first choice for the backs and sides. However, the cypress tree is relatively small, and good quality wood for guitars is not easy to obtain; frequently Alaskan Yellow Cedar ( chamaecyparis nootkatensis ) and even laminated Sycamore is used as a substitute.
For solid-body electric guitars, the solid wood used for good quality instruments varies, but Ash , specifically Swamp Ash , is often preferred for its tonal and visual aspects. Swamp Ash is quite heavy, but has a striking grain. A common substitute is Alder , especially for finishes that are not transparent. Alder is often used in laminated form for solid bodies as well. Mahogany , more expensive and rare than Swamp Ash and Alder, is also a premium choice for solid bodies, frequently topped with a Maple veneer, often fancy, with flamed or “quilted (curly)” grain.
The wood selected for a guitar's back and sides is not as significant a factor in its sound as the quality of the soundboard or top. As confirmation, a number of guitars currently use synthetic materials for the back and sides, with a surprisingly good result.
Different wood combinations used with the same good design will result in instruments that have a different sound. Some designs with specific wood combinations result in guitars which are ideal for certain playing styles.
One guitar maker referred to his company's mahogany dreadnaught, when made with a red spruce ( Adirondack ) top, as “a bluegrass machine”!
We have been intrigued with cedar tops on certain steel-string acoustic models for fingerstyle playing.
The backs and sides of most classical guitars are made with rosewood, mahogany being used primarily for student models. Maple has been used for the back and sides of classical guitars from their earliest years, but is rarely seen today because rosewood is perceived as giving the guitar a more powerful sound for the concert hall; likewise, walnut is sometimes used on classical guitars, but is seldom seen on concert models.
The variety of wood selected for a guitar is only the first criterion. More important is the quality of the selection. Getting enough wood in good grades is a great challenge for guitar makers. Although good materials are critical for making a good guitar, in our opinion, guitar design and the execution of that design are even more critical. (See What makes one guitar cost more than another?)