Tonewood refers to specific wood varieties used for woodwind or acoustic stringed instruments.
According to Mottola's Cyclopedic Dictionary of Lutherie Terms, tonewood is:Wood that is used to make stringed musical instruments.
The term is often used to indicate wood species that are suitable for stringed musical instruments and, by exclusion, those that are not.
[1]As a rough generalization it can be said that stiff-but-light softwoods (i.e. from coniferous trees) are favored for the soundboards or soundboard-like surface that transmits the vibrations of the strings to the ambient air.
Woods used for woodwind instruments include African blackwood, (Dalbergia melanoxylon), also known as grenadilla, used in modern clarinets and oboes.
Flexural modulus GPa Poisson's strain ratio Flexural strength MPa Compress strength MPa Shrink Volume % Sound radiation coefficient Rigidity 3mm plate N·m basswood (Linden, Lime) CFRP, glass, aluminium, and steel added for comparison, since they are sometimes used in musical instruments.
[10] Most professional luthiers will build at 8% moisture content (45% relative humidity), and such wood weighs less on average than that reported here, since it contains less water.
The shrink volume percent shown here is the amount of shrinkage in all three dimensions as the wood goes from green to oven-dry.
However, the stability of tuning is primarily due to the length-wise shrinkage of the neck, which is typically only about 0.1% to 0.2% green to dry.
The shrinkage of the length of the neck, as a percent, is quite a bit less, but given the dimension, it is enough to affect the pitch of the strings.
The loudest wood tops, such as Sitka Spruce, are lightweight and stiff, while maintaining the necessary strength.
—in short, the higher this number for a given wood species, the less a neck will deflect under a given force (i.e. from the strings).
Spruce, for example, is very common, but large pieces with even grain represent a small proportion of total supply and can be expensive.
Some tonewoods are particularly hard to find on the open market, and small-scale instrument makers often turn to reclamation,[16][17] for instance from disused salmon traps in Alaska, various old construction in the U.S Pacific Northwest, from trees that have blown down, or from specially permitted removals in conservation areas where logging is not generally permitted.
[18] Mass market instrument manufacturers have started using Asian and African woods, such as bubinga (Guibourtia species) and wenge (Millettia laurentii), as inexpensive alternatives to traditional tonewoods.
The Fiemme Valley, in the Alps of Northern Italy, has long served as a source of high-quality spruce for musical instruments,[19] dating from the violins of Antonio Stradivari to the piano soundboards of the contemporary maker Fazioli.
Guitar makers generally favor quartersawn wood because it provides added stiffness and dimensional stability.
Some guitar manufacturers subject the wood to rarefaction, which mimics the natural aging process of tonewoods.
Guitar builders using torrefied soundboards claim improved tone, similar to that of an aged instrument.
Softwoods such as spruce, cedar, and redwood, which are commonly used for guitar soundboards, are easier to torrefy than hardwoods, such as maple.
On inexpensive guitars, it is increasingly common to use roseacer for the fretboard, which mimics rosewood, but is actually a form of thermally-modified maple.
However, while engineering tests of the thermally-modified wood indicated increased resistance to humidity, they also showed a significant reduction in strength (ultimate breaking point), while stiffness (flexural modulus) remained the same or was slightly reduced.
[21][22] Although the reduction in strength can be controlled by reducing the temperature of the process, the manufacturer recommends not using its product for structural purposes.
However, it is perhaps possible to compensate for this loss of strength in guitars by using carbon-fiber stiffeners in necks and increased bracing in tops.