More About Wood
Obviously, classical guitars like many guitars are constructed from wood. Several different species are used and the choice of material reflects the purpose of the part. For example, various species of softwoods are used for the top, mainly because they combine a degree of stiffness with sufficiently light weight and durability. Backs and sides are often a hardwood (not always), and can range from Mahogany to Cypress to Rosewood, to Koa to Cocobolo. Necks are frequently mahogany or Spanish Cedar.
Often wood used for aircraft construction finds its way into guitar tops, including various species of Spruce and Cedar. These combine light weight with good stiffness and strength. Some softwoods are difficult to use as topwoods because their weight becomes excessive when compared to their stiffness. Tonewood choice is always a balancing act.
Backs and sides are made usually from a species of Rosewood, commonly East Indian (Dalbergia latifolia) Other Rosewoods have been used such as Brazilian Rosewood (Dalbergia nigra), and Madagascan Rosewood (Dalbergia Maritima) these woods have durability, strength and beauty, and in the case of Indian Rosewood stability. The beautiful black lines on Brazilian Rosewood often seem to act as if “crack here” should be marked on the wood. The tonality of the Rosewood family seems to have been established by practice. Other woods of similar characteristics will work too. Some people will insist on a certain species; if it works for them, ok.
Naturally, we might anticipate a great deal of difference in sound characteristics between the various species used in the construction of the body of the instrument. Our own experience has been markedly different. Conventional wisdom makes producing the sound quality of an instrument to be a sort of wood alchemy, where the right mixture of species will produce a particular sound. We have used different species. and found the differences to be very subtle; so subtle that when three of our instruments were played to listeners by the same individual; the owners of the instruments could not pick their own guitars out, and they could not discern Cedar from Spruce. Given that the sample size is small perhaps this is an anomaly, but I think the sound differences between species are probably more hype than reality. My father and I used to joke about wood that was cut at the full moon on the north side of the mountain on a steep slope and how that would be touted as the only wood to use. People of course would pay accordingly.
Another idea that has some basis in reality is the fact that wood with finer grain is often sought after. There are sometimes desirable strength properties that come with such grain. But often there are other penalties in the physical characteristics that cancel this gain. Other than making it very difficult to find the center joint when the grain is so fine, I haven’t found appreciable difference between the most even and fine grained topwoods (like a “master” grade), and what might be considered (AAA or even AA grade wood). The guitarmaker will have a lot more to do with the sound than the “superb” materials.
Another factor to consider in choosing the wood has to do with the durability of the instrument. Wood continues to respond to humidity for its entire lifetime, and so woods which exhibit greater dimensional stability with humidity changes have advantages. Western Red cedar has a dimensional change across the grain of about half that of typical spruce species. The price paid for that is an extreme softness of the wood. It dents very easily in comparison to spruce, and so may require better physical protection where the player’s fingernails may touch the top.