Tonewood

Tonewood refers to specific wood varieties used for woodwind or acoustic stringed instruments. The word implies that certain species exhibit qualities that enhance acoustic properties of the instruments, but other properties of the wood such as aesthetics and availability have always been considered in the selection of wood for musical 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. But the list of species generally considered to be tonewoods changes constantly and has changed constantly throughout history.

Varieties of tonewood

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. Hardwoods (i.e. from deciduous trees) are favored for the body or framing element of an instrument. Woods used for woodwind instruments include African blackwood, (Dalbergia melanoxylon), also known as grenadilla, used in modern clarinets and oboes. Bassoons are usually made of Maple, especially Norway maple (Acer platanoides). Wooden flutes, recorders, and baroque and classical period instruments may be made of various hardwoods, such as pear (Pyrus species), boxwood (Buxus species), or ebony (Diospyros species).

Softwoods

• Spruces are often used in the soundboards of instruments from the lute, violin, oud, mandolin, guitar, and harpsichord families; as well as the piano. Spruce is particularly suited for this use because of its high stiffness-to-weight ratio. Commonly used varieties are Sitka (or Alaskan) spruce (Picea sitchensis), Adirondack (or red) spruce (Picea rubens), Engelmann spruce (Picea engelmannii), and Picea abies (variously known as Norwegian, German, Alpine, Italian or European spruce).
• Cedars, particularly western red cedar (Thuja plicata, not a true cedar), have since the 1950s been used in the tops of flamenco guitars, classical guitars and to a less degree in steel string acoustic guitars.
• Yew was once widely used for lute bowls.
• Other softwoods, such as redwood and Douglas-fir have been used to a limited degree. Redwood is not used commonly for guitars with steel strings, but has been used for classical guitars.

Hardwoods

• Maple, especially Norway Maple, is traditionally used for the backs and sides of violin family instruments. Bosnian Maple is probably the maple used by the Italian violin makers Stradivari and Guarneri. Maple is also frequently seen in acoustic guitars and mandolins. Most Fender electric guitars feature maple necks (it is one of the hardest and most stable tonewoods, so it is often used in the neck because of its ability to withstand high string tension). Hard maple is commonly used for wooden tripods for its vibration damping properties. Variations of maple (commonly maple wood with flamed or quilted grains) are used on the tops of electric guitars for aesthetic purposes. The very sturdy frame of the modern piano is usually made of maple or of beech.
• Mahogany may be used in the tops of some guitars as well as the back, sides, and necks of instruments of the mandolin and guitar families. Mahogany may also be used for the solid bodies of electric guitars, such as the Gibson Les Paul. Due to lack of availability, other similar woods are used as mahogany replacements, such as Australian red cedar, Toona sureni, African mahogany (Khaya), meranti (Lauan), Kauri (Agathis), mora (Nato), sapele, nyatoh and okoume. Some of these alternatives are mahogany family timbers.
• Rosewoods are often used in the back and/or sides of guitars and mandolins and fretboards on guitars. The most sought-after variety, Brazilian rosewood (Dalbergia nigra) has become scarce and expensive due to severe trade restrictions (embargo and CITES), scarcity and demand. However, in August 2019, CITES announced an exception for rosewood used in musical instruments. The most widely used rosewood used now is East Indian Rosewood, often paired with a spruce top for steel string guitars and with spruce or cedar for classical guitars. Another rosewood, cocobolo, is used in upper-end clarinets and guitars.
• Koa is traditionally used for ukuleles. Koa is also used for steel string guitars mostly due to its beauty and compressed dynamic range.
• Ebony is also often used in many types of instruments for fingerboards, tailpieces, tuning pegs, and so forth due to its attractive appearance, smoothness to the touch, hardness and wear resistance. Several varieties of ebony are used. Ebony is often dyed to make it appear more uniformly black than the natural wood, which sometimes shows brown streaks.
• Paubrasilia, commonly called Pernambuco or Brazilwood, is the most sought-after material for the bows of classical stringed instruments, because of its effects on the tones they produce.
• Blackwood (Tasmanian/Australian).
• Walnut is often used for the backs and sides of guitars and mandolin family instruments.
• Ash, Alder and Basswood are commonly used for the bodies of electric guitars, ash for its light-colored, natural wood finishes, and alder and basswood for their uniform density, their ease of machining, and amenability to rapid finishing techniques.

Mechanical properties of tonewoods

Some of the mechanical properties of common tonewoods, sorted by density. See also Physical properties of wood.

Wood species	ρ Density kg/m3	J Hardness N	ELR Flexural modulus GPa	𝜈LR Poisson's strain ratio	F Flexural strength MPa	C Compress strength MPa	S Shrink Volume %	R Sound radiation coefficient	D Rigidity 3mm plate N·m
Balsa	150	300	3.71	0.229	19.6	11.6	8.5	33.2	8.8
Paulownia	280	1330	4.38		37.8	20.7	6.4	14.1
Northern White Cedar	350	1420	5.52	0.337	44.8	27.3	7.2	11.3	14.0
King Billy Pine	350		5.80		69.0			11.6
Sugi (Japanese Cedar)	360	1420	7.65		36.4	28.0	10.5	12.8
Western Red Cedar	370	1560	7.66	0.378	51.7	31.4	6.8	12.3	20.1
Obeche	380	1910	6.69		60.8	29.3	8.7	11.0
Engelmann Spruce	385	1740	9.44	0.422	62.2	31.5	11.0	12.9	25.8
Black Cottonwood	385	1560	8.76		58.6	31.0	12.4	12.4
Sugar Pine	400	1690	8.21	0.356	56.6	30.8	7.9	11.3	21.2
Eastern White Pine	400	1690	8.55		59.3	33.1	8.2	11.6
Norway Spruce	405	1680	9.70		63.0	35.5	12.9	12.0
American Basswood (Linden, Lime)	415	1824	10.07	0.364	60.0	32.6	15.8	11.9	26.1
Coast Redwood	415	2000	8.41	0.360	61.7	39.2	6.9	10.8	21.7
Black Willow	415	1920	6.97		53.8	28.3	13.9	9.9
White Fir	415	2140	10.24		66.9	39.6	9.8	12.0
Noble Fir	415	1820	11.17		74.4	39.5	12.4	12.5
Sitka Spruce	425	2270	11.03	0.372	70.0	38.2	11.5	12.0	28.8
White Spruce	425	2140	9.07		59.6	32.6	13.7	10.9
Okoume	430	1790	8.47		75.0	36.2	12.2	10.3
Red Spruce (Adirondack)	435	2180	10.76		66.0	33.6	11.8	11.4
Western White Pine	435	1870	10.07	0.329	66.9	34.8	11.8	11.1	25.4
California Red Fir	435	2220	10.23		71.5	37.3	11.4	11.1
Butternut	435	2180	8.14		55.9	35.2	10.6	9.9
White Poplar	440	1820	8.90	0.344	65.0	NA	8.4	10.2	22.7
Red Alder	450	2620	9.52		67.6	40.1	12.6	10.2
Yellow Poplar	455	2400	10.90	0.318	69.7	38.2	12.7	10.8	27.3
Catalpa	460	2450	8.35		64.8	18.9	7.3	9.3
Port Orford Cedar	465	2620	11.35	0.378	84.8	41.9	10.1	10.6	29.8
Primavera	465	3170	7.81		70.5	40.4	8.6	8.8
Western Hemlock	465	2400	11.24	0.485	77.9	37.3	12.4	10.6	33.1
Spanish Cedar	470	2670	9.12		70.8	40.4	10.2	9.4
Australian Red Cedar (Toona)	485	3130	9.22		71.5	36.1	10.8	9.0
Swamp Ash	481-538
European Alder (Black Alder)	495	2890	8.99		75.9	42.2	11.0	8.6
Alaskan Yellow Cedar	495	2580	9.79		76.6	43.5	9.2	9.0
Sassafras	495	2800	7.72		62.1	45.5	10.3	8.0
Douglas Fir	510	2760	12.17	0.292	86.2	47.9	11.6	9.6	29.9
Bald Cypress	515	2270	9.93	0.338	73.1	43.9	10.5	8.5	25.2
Silver Maple	530	3110	7.86		61.4	36.0	12.0	7.3
Mediterranean Cypress	535	2490	5.28		44.6			5.9
Kauri (Agathis)	540	3230	11.87		86.6	42.3	11.3	8.7
Black Ash	545	3780	11.00		86.9	41.2	15.2	8.2
American Sycamore	545	3430	9.79		69.0	37.1	14.1	7.8
Bigleaf Maple	545	3780	10.00		73.8	41.0	11.6	7.9
Sweetgum	545	3780	11.31	0.325	86.2	43.6	15.8	8.4	28.5
Anigre	550	4380	10.95		83.0	47.7	11.8	8.1
Limba (Korina)	555	2990	10.49		86.2	45.4	10.8	7.8
Black Cherry	560	4230	10.30	0.392	84.8	49.0	11.5	7.7	27.4
Cerejeira	560	3510	10.88		72.9	43.5	8.3	7.9
Queensland Maple	560	3620	10.83		81.0	47.0	15.0	7.9
American Elm	560	3690	9.24		81.4	38.1	14.6	7.3
Western Larch	575	3690	12.90	0.355	89.7	52.6	14.0	8.2	33.2
Avodiré	575	5180	11.13		106.2	51.7	11.3	7.7
Lacewood	580	3740
Honduran Mahogany	590	4020	10.06	0.314	80.8	46.6	7.5	7.0	25.1
Monkeypod	600	4010	7.9		65.7	39.9	6.0	6.1
Cuban Mahogany	600	4120	9.31		74.4	43.3	8.0	6.6
Peruvian Walnut	600	4250	7.81		77.0	45.2	11.4	6.0
Red Elm	600	3830	10.28		89.7	43.9	13.8	6.9
Red Maple	610	4230	11.31	0.434	92.4	45.1	12.6	7.1	31.4
Black Walnut	610	4490	11.59	0.495	100.7	52.3	12.8	7.1	34.5
Koa	610	5180	10.37		87.0	48.7	12.4	6.8
Sycamore Maple (EU)	615	4680	9.92		98.1	55.0	12.3	6.5
California Black Oak	620	4840	6.76		59.4	38.9	10.2	5.3
Nyatoh	620	4760	13.37		96.0	54.4	8.7	7.5
Oregon Myrtle	635	5650	8.45		66.9	38.9	11.9	5.7
English Walnut	640	5410	10.81		111.5	50.2	13.0	6.4
Green Ash	640	5340	11.40		97.2	48.8	12.5	6.6
Australian Blackwood	640	5180	14.82		103.6	41.0	11.9	7.5
African Mahogany (Khaya)	640	4760	10.60		91.0	49.0	10.0	6.4
Redheart	640	5380	10.32		98.7	46.2	10.6	6.3
Claro Walnut (California Black Walnut)	640	5030					10.7
Norway Maple	645	4510	10.60		115.0	59.0		6.3
Teak	655	4740	12.28		97.1	54.8	7.2	6.6
Narra	655	5620	11.89		96.3	57.0	6.9	6.5
Iroko	660	5610	9.38		87.6	54.0	8.8	5.7
Sapele	670	6280	12.04		109.9	60.4	12.8	6.3
White Ash	675	5870	12.00	0.371	103.5	51.1	13.3	6.2	31.3
Dark Red Meranti (Lauan)	675	3570	12.02		87.7	48.8	12.5	6.3
European Ash	680	6580	12.31		103.6	51.0	15.3	6.3
Makore	685	5350	10.71		112.6	57.2	12.4	5.8
Yellow Birch	690	5610	13.86	0.426	114.5	56.3	16.8	6.5	38.1
Pear	690	7380	7.80		83.3	44.1	13.8	4.9
Field Maple	690	5110	11.80		123.0			6.0
Red Oak	700	5430	12.14	0.350	99.2	46.8	13.7	5.9	31.1
Hard Maple (Sugar, Rock)	705	6450	12.62	0.424	109.0	54.0	14.7	6.0	34.6
European Beech	710	6460	14.31		110.1	57.0	17.3	6.3
American Beech	720	5780	11.86		102.8	51.1	17.2	5.6
Afrormosia	725	6980	11.83		102.9	66.0	9.9	5.6
Pecan	735	8100	11.93		94.5	54.1	13.6	5.5
African Padauk	745	8760	11.72		116.0	56.0	7.6	5.3
Keruing (Apitong)	745	6170	15.81		115.2	61.4	16.3	6.2
White Oak	755	5990	12.15	0.369	102.3	50.8	16.3	5.3	31.6
Black siris	760	7260	11.8		96.4	56.1	12.3	5.2
Black Locust	770	7560	14.14		133.8	70.3	10.2	5.6
Tzalem	780	6230	13.10		88.3		9.5	5.3
Plum	795	6900	10.19		88.4			4.5
Zebrawood	805	8160	16.37		122.8	63.5	17.8	5.6
Ziricote	805	8780	10.93		113.1	63.9	9.8	4.6
Ovangkol (Shedua, Amazique)	825	5900	18.60		140.3	64.2	12.1	5.8
Yellowheart	825	7950	16.64		115.9	69.5	12.0	5.4
East Indian Rosewood	830	10870	11.50		114.4	59.7	8.5	4.5
Canarywood	830	6750	14.93		131.6	67.2	8.4	5.1
Brazilian Rosewood	835	12410	13.93		135.0	67.2	8.5	4.9
Partridgewood	835	7960	18.17		127.5	64.1	12.3	5.6
Pignut Hickory	835	9520	15.59		138.6	63.4	17.5	5.2
Indian Laurel	855	10390	12.46		101.4	56.7	13.2	4.5
Osage Orange	855	11640	11.64		128.6	64.7	9.2	4.3
Bocote	855	8950	12.19		114.4	59.4	11.6	4.4
Pau Ferro	865	8710	10.86		122.4	60.9	9.9	4.1
Wenge	870	8600	17.59		151.7	80.7	12.9	5.2
Panga Panga	870	7310	15.73		131.2	75.1	10.5	4.9
Leopardwood	885	9560	19.91			50.2	11.5	5.4
Bubinga	890	10720	18.41		168.3	75.8	13.9	5.1
Purpleheart (Amaranth)	905	11190	20.26		151.7	83.7	10.6	5.2
Gonçalo Alves	905	9640	16.56		117.0	74.2	11.2	4.7
Jatoba	910	11950	18.93		155.2	81.2	12.1	5.0
Santos Mahogany	915	10680	16.41		148.7	80.6	10.0	4.6
Madagascar Rosewood	935	12080	12.01		165.7	76.6	10.3	3.8
Macacauba (Granadillo)	950	12030	19.6		148.6	80.7	7.2	4.8
Gaboon Ebony	955	13700	16.89		158.1	76.3	19.6	4.4
Boxwood	975	12610	17.20		144.5	68.6	15.8	4.3
Brazilwood (Pernambuco)	980	12540	17.55		179.4		13.3	4.3
Chechen	990	10010					10.8
Mora (Nato)	1015	10230	19.24		155.5	82.4	17.7	4.3
Curapay	1025	16150	18.04		193.2	94.4	12.0	4.1
Honduran Rosewood	1025	9790	22.00					4.5
Pau Rosa	1030	13080	17.10		166.2	92.8	10.7	4.0
Bloodwood	1050	12900	20.78		174.4	98.7	11.7	4.2
Bulletwood (Massaranduba)	1080	13920	23.06		192.2	89.2	16.8	4.3
Cumaru	1085	14800	22.33		175.1	95.5	12.6	4.2
Cocobolo	1095	14140	18.70		158.0	81.3	7.0	3.8
Ipê	1100	15620	22.07		177.0	93.8	12.4	4.1
Macassar Ebony	1120	14140	17.35		157.2	80.2	-	3.5
Katalox (Mexican Royal Ebony)	1150	16260	25.62		193.2	105.1	11.2	4.1
Snakewood	1210	16900	23.2		195	119	10.7	3.6
Lignum Vitae	1260	19510	14.09		127.2	84.1	14.0	2.7
African Blackwood (Grenadilla)	1270	16320	17.95		213.6	72.9	7.7	3.0
Carbon-fiber/Epoxy	1600		135	0.30	1500	1200	0	5.7	334
Common flat glass	2530		74				0	2.1
Aluminum Alloy	2700		68	0.33			0	1.9	172
Steel Alloy	8000		200	0.30			0	0.6	495

Carbon-fiber/Epoxy, glass, aluminum, and steel added for comparison, since they are sometimes used in musical instruments.

Density is measured at 12% moisture content of the wood, i.e. air at 70 °F and 65% relative humidity. Most professional luthiers will build at 8% moisture content (45% relative humidity), and such wood would weigh less on average than that reported here, since it contains less water.

Data comes from the Wood Database, except for 𝜈_LR, Poisson's ratio, which comes from the Forest Product Laboratory, United States Forest Service, United States Department of Agriculture. The ratio displayed here is for deformation along the radial axis caused by stress along the longitudinal axis.

The shrink volume percent shown here is the amount of shrinkage in all three dimensions as the wood goes from green to oven-dry. This can be used as a relative indicator of how much the dry wood will change as humidity changes, sometimes referred to as the instrument's "stability". 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 volume shrinkage is mostly due to the radial and tangential shrinkage. In the case of a neck (quarter-sawn), the radial shrinkage affects the thickness of the neck, and the tangential shrinkage affects the width of the neck. Given the dimensions involved, this shrinkage should be practically unnoticeable. 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 sound radiation coefficient is defined as:

$R={\sqrt {\cfrac {E}{{\rho }^{3}}}}$

where $E$ is flexural modulus in Pascals (i.e. the number in the table multiplied by 10⁹), and ρ is the density in kg/m³, as in the table.

From this, it can be seen that the loudness of the top of a stringed instrument increases with stiffness, and decreases with density. The loudest wood tops, such as Sitka Spruce, are lightweight and stiff, while maintaining the necessary strength. Denser woods, for example Hard Maple, often used for necks, are stronger but not as loud (R = 6 vs. 12).

When wood is used as the top of an acoustic instrument, it can be described using plate theory and plate vibrations. The flexural rigidity of an isotropic plate is:

$D={\cfrac {EH^{3}}{12(1-\nu ^{2})}}$

where $E$ is flexural modulus for the material, $H$ is the plate thickness, and $\nu$ is Poisson's ratio for the material. Plate rigidity has units of Pascal·m³ (equivalent to N·m), since it refers to the moment per unit length per unit of curvature, and not the total moment. Of course, wood is not isotropic, it's orthotropic, so this equation describes the rigidity in one orientation. For example, if we use 𝜈LR, then we get the rigidity when bending on the longitudinal axis (with the grain), as would be usual for an instrument's top. This is typically 10 to 20 times the cross-grain rigidity for most species.

The value for $D$ shown in the table was calculated using this formula and a thickness $H$ of 3.0mm=0.118″, or a little less than 1/8".

When wood is used as the neck of an instrument, it can be described using beam theory. Flexural rigidity of a beam (defined as $EI$) varies along the length as a function of x shown in the following equation:

$\ EI{dy \over dx}\ =\int _{0}^{x}M(x)dx+C_{1}$

where $E$ is the flexural modulus for the material, $I$ is the second moment of area (in m⁴), $y$ is the transverse displacement of the beam at x, and $M(x)$ is the bending moment at x. Beam flexural rigidity has units of Pascal·m⁴ (equivalent to N·m²).

The amount of deflection at the end of a cantilevered beam is:

$w_{C}={\tfrac {PL^{3}}{3EI}}$

where $P$ is the point load at the end, and $L$ is the length. So deflection is inversely proportional to $EI$. Given two necks of the same shape and dimensions, $I$ becomes a constant, and deflection becomes inversely proportional to $E$—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).

Read more about mechanical properties in Wood for Guitars.

Selection of tonewoods

In addition to perceived differences in acoustic properties, a luthier may use a tonewood because of:

• Availability
• Stability
• Cosmetic properties such as the color or grain of the wood
• Tradition
• Size (Some instruments require large pieces of suitable wood)

Sources

Many tonewoods come from sustainable sources through specialist dealers. 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, 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. 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, dating from the violins of Antonio Stradivari to the piano soundboards of the contemporary maker Fazioli.

Preparation

Tonewood choices vary greatly among different instrument types. Guitar makers generally favor quartersawn wood because it provides added stiffness and dimensional stability. Soft woods, like spruce, may be split rather than sawn into boards so the board surface follows the grain as much as possible, thus limiting run-out.

For most applications, wood must be dried before use, either in air or kilns. Some luthiers prefer further seasoning for several years. Wood for instruments is typically used at 8% moisture content (which is in equilibrium with air at 45% relative humidity). This is drier than usually produced by kilns, which is 12% moisture content (65% relative humidity). If an instrument is kept at a humidity that is significantly lower than that at which it was built, it may crack. Therefore, valuable instruments must be contained in controlled environments to prevent cracking, especially cracking of the top.

Some guitar manufacturers subject the wood to rarefaction, which mimics the natural aging process of tonewoods. Torrefaction is also used for this purpose, but it often changes the cosmetic properties of the wood. 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 a product called "Roseacer" for the fretboard, which mimics Rosewood, but is actually a thermally-modified Maple.

"Roasted" Maple necks are increasingly popular as manufacturers claim increased stiffness and stability in changing conditions (heat and humidity). However, while engineering tests of the ThermoWood method 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. 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.

External links

• Commercial article on woods used for woodwind instruments
• Guitarbench's database of tonewood species
• Alan Arnold Interactive Tonewood guide
• The Heretics Guide to Tonewoods
• More about Guitar Wood
• Tonewoods for guitars
• Taylor acoustic guitar woods