Tonewood

Last updated

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:

Contents

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. [1]

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, oboes, and wooden concert flutes. Bassoons are usually made of hard maples, especially Norway maple ( Acer platanoides), but sometimes palisander and rosewoods ( Dalbergia spp.) is used in older or French-system bassoons. Wooden flutes, recorders, oboes, and early clarinet-like wind instruments of baroque and classical periods may be made of various hardwoods, such as Pear ( Pyrus spp.), Boxwood ( Buxus spp.), or Ebony ( Diospyros spp.).

Softwoods

Hardwoods

Mechanical properties of tonewoods

Some of the mechanical properties of common tonewoods, sorted by density.

Wood speciesρ

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 1503003.710.22919.611.68.533.28.8
Paulownia 2801,3304.3837.820.76.414.1
Northern white cedar 3501,4205.520.33744.827.37.211.314.0
King Billy pine [13] 3505.8069.011.6
Sugi (Japanese cedar)3601,4207.6536.428.010.512.8
Western red cedar 3701,5607.660.37851.731.46.812.320.1
Obeche 3801,9106.6960.829.38.711.0
Engelmann spruce 3851,7409.440.42262.231.511.012.925.8
Black cottonwood 3851,5608.7658.631.012.412.4
Sugar pine 4001,6908.210.35656.630.87.911.321.2
Eastern white pine 4001,6908.5559.333.18.211.6
Norway spruce 4051,6809.7063.035.512.912.0
American basswood (Linden, Lime)4151,82410.070.36460.032.615.811.926.1
Coast redwood 4152,0008.410.36061.739.26.910.821.7
Black willow 4151,9206.9753.828.313.99.9
White fir 4152,14010.2466.939.69.812.0
Noble fir 4151,82011.1774.439.512.412.5
Sitka spruce 4252,27011.030.37270.038.211.512.028.8
White spruce 4252,1409.0759.632.613.710.9
Okoume 4301,7908.4775.036.212.210.3
Red spruce 4352,18010.7666.033.611.811.4
Western white pine 4351,87010.070.32966.934.811.811.125.4
California red fir 4352,22010.2371.537.311.411.1
Butternut 4352,1808.1455.935.210.69.9
White poplar 4401,8208.900.34465.0NA8.410.222.7
Red alder 4502,6209.5267.640.112.610.2
Yellow poplar 4552,40010.900.31869.738.212.710.827.3
Catalpa 4602,4508.3564.818.97.39.3
Port Orford cedar 4652,62011.350.37884.841.910.110.629.8
Primavera 4653,1707.8170.540.48.68.8
Western hemlock 4652,40011.240.48577.937.312.410.633.1
Spanish cedar 4702,6709.1270.840.410.29.4
Australian red cedar 4853,1309.2271.536.110.89.0
Swamp ash 481–538
European alder 4952,8908.9975.942.211.08.6
Alaskan yellow cedar 4952,5809.7976.643.59.29.0
Sassafras 4952,8007.7262.145.510.38.0
Douglas fir 5102,76012.170.29286.247.911.69.629.9
Bald cypress 5152,2709.930.33873.143.910.58.525.2
Cedar of Lebanon 5203,67010.1824210.48.5
Silver maple 5303,1107.8661.436.012.07.3
Mediterranean cypress 5352,4905.2844.65.9
Kauri 5403,23011.8786.642.311.38.7
Black ash 5453,78011.0086.941.215.28.2
American sycamore 5453,4309.7969.037.114.17.8
Bigleaf maple 5453,78010.0073.841.011.67.9
Sweetgum 5453,78011.310.32586.243.615.88.428.5
Anigre 5504,38010.9583.047.711.88.1
Limba 5552,99010.4986.245.410.87.8
Black cherry 5604,23010.300.39284.849.011.57.727.4
Cerejeira 5603,51010.8872.943.58.37.9
Queensland maple 5603,62010.8381.047.015.07.9
American elm 5603,6909.2481.438.114.67.3
Western larch 5753,69012.900.35589.752.614.08.233.2
Avodiré 5755,18011.13106.251.711.37.7
Lacewood 5803,740
Honduran mahogany 5904,02010.060.31480.846.67.57.025.1
Monkeypod 6004,0107.965.739.96.06.1
Cuban mahogany 6004,1209.3174.443.38.06.6
Peruvian walnut 6004,2507.8177.045.211.46.0
Red elm 6003,83010.2889.743.913.86.9
Red maple 6104,23011.310.43492.445.112.67.131.4
Black walnut 6104,49011.590.495100.752.312.87.134.5
Koa 6105,18010.3787.048.712.46.8
Sycamore Maple 6154,6809.9298.155.012.36.5
California black oak 6204,8406.7659.438.910.25.3
Nyatoh 6204,76013.3796.054.48.77.5
Oregon myrtle 6355,6508.4566.938.911.95.7
English walnut 6405,41010.81111.550.213.06.4
Green ash 6405,34011.4097.248.812.56.6
Australian blackwood 6405,18014.82103.641.011.97.5
African mahogany 6404,76010.6091.049.010.06.4
Redheart 6405,38010.3298.746.210.66.3
Claro walnut 6405,03010.7
Norway maple 6454,51010.60115.059.06.3
Teak 6554,74012.2897.154.87.26.6
Narra 6555,62011.8996.357.06.96.5
Iroko 6605,6109.3887.654.08.85.7
Sapele 6706,28012.04109.960.412.86.3
White ash 6755,87012.000.371103.551.113.36.231.3
Dark red meranti 6753,57012.0287.748.812.56.3
European ash 6806,58012.31103.651.015.36.3
Makore 6855,35010.71112.657.212.45.8
Yellow birch 6905,61013.860.426114.556.316.86.538.1
Pear 6907,3807.8083.344.113.84.9
Field maple 6905,11011.80123.06.0
Red oak 7005,43012.140.35099.246.813.75.931.1
Hard maple 7056,45012.620.424109.054.014.76.034.6
European beech 7106,46014.31110.157.017.36.3
American beech 7205,78011.86102.851.117.25.6
Afrormosia 7256,98011.83102.966.09.95.6
Pecan 7358,10011.9394.554.113.65.5
African padauk 7458,76011.72116.056.07.65.3
Keruing 7456,17015.81115.261.416.36.2
White oak 7555,99012.150.369102.350.816.35.331.6
Black siris 7607,26011.896.456.112.35.2
Black locust 7707,56014.14133.870.310.25.6
Tzalem 7806,23013.1088.39.55.3
Plum 7956,90010.1988.44.5
Zebrawood 8058,16016.37122.863.517.85.6
Ziricote 8058,78010.93113.163.99.84.6
Ovangkol 8255,90018.60140.364.212.15.8
Yellowheart 8257,95016.64115.969.512.05.4
East Indian rosewood 83010,87011.50114.459.78.54.5
Canarywood 8306,75014.93131.667.28.45.1
Brazilian rosewood 83512,41013.93135.067.28.54.9
Partridgewood 8357,96018.17127.564.112.35.6
Pignut hickory 8359,52015.59138.663.417.55.2
Indian laurel 85510,39012.46101.456.713.24.5
Osage orange 85511,64011.64128.664.79.24.3
Bocote 8558,95012.19114.459.411.64.4
Pau ferro 8658,71010.86122.460.99.94.1
Wenge 8708,60017.59151.780.712.95.2
Panga panga 8707,31015.73131.275.110.54.9
Leopardwood 8859,56019.9150.211.55.4
Bubinga 89010,72018.41168.375.813.95.1
Purpleheart 90511,19020.26151.783.710.65.2
Gonçalo alves 9059,64016.56117.074.211.24.7
Jatoba 91011,95018.93155.281.212.15.0
Santos mahogany 91510,68016.41148.780.610.04.6
Madagascar rosewood 93512,08012.01165.776.610.33.8
Macacauba 95012,03019.6148.680.77.24.8
Gaboon ebony 95513,70016.89158.176.319.64.4
Boxwood 97512,61017.20144.568.615.84.3
Brazilwood 98012,54017.55179.413.34.3
Chechen 99010,01010.8
Mora 1,01510,23019.24155.582.417.74.3
Curapay 1,02516,15018.04193.294.412.04.1
Honduran rosewood 1,0259,79022.004.5
Pau rosa 1,03013,08017.10166.292.810.74.0
Bloodwood 1,05012,90020.78174.498.711.74.2
Bulletwood 1,08013,92023.06192.289.216.84.3
Cumaru 1,08514,80022.33175.195.512.64.2
Cocobolo 1,09514,14018.70158.081.37.03.8
Ipê 1,10015,62022.07177.093.812.44.1
Macassar ebony 1,12014,14017.35157.280.2-3.5
Katalox 1,15016,26025.62193.2105.111.24.1
Snakewood 1,21016,90023.219511910.73.6
Lignum vitae 1,26019,51014.09127.284.114.02.7
African blackwood 1,27016,32017.95213.672.97.73.0
CFRP 1,6001350.301500120005.7334
Common flat glass 2,5307402.1
Aluminium alloy 2,700680.3301.9172
Steel alloy 8,0002000.3000.6495

CFRP, glass, aluminium, 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 (21°C) and 65% relative humidity. [14] 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.

Data comes from the Wood Database, [15] except for 𝜈LR, Poisson's ratio, which comes from the Forest Product Laboratory, United States Forest Service, United States Department of Agriculture. [16] 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. [17] 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 [18] as:

where 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:

where is flexural modulus for the material, is the plate thickness, and 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. Wood is not isotropic, but orthotropic, so this equation describes the rigidity in one orientation. For example, using 𝜈LR, one gets 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 shown in the table was calculated using this formula and a thickness of 3 mm.

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

where is the flexural modulus for the material, is the second moment of area (in m4), is the transverse displacement of the beam at x, and 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:

where is the point load at the end, and is the length. So deflection is inversely proportional to . Given two necks of the same shape and dimensions, becomes a constant, and deflection becomes inversely proportional to —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. [19]

Selection of tonewoods

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

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, [20] [21] 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. [22] 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, [23] 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. This is especially important for braces because it maximizes their strength.

For most applications, wood must be dried before use, either in air or kilns. [24] 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 roseacer for the fretboard, which mimics rosewood, but is actually a form of 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 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. [25] [26] 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.

References

  1. Mottola, R.M. (1 January 2020). Mottola's Cyclopedic Dictionary of Lutherie Terms. LiutaioMottola.com. p. 165. ISBN   978-1-7341256-0-3.
  2. "Tonewoods". Joh.deHeer!. Retrieved 2024-11-11.
  3. "Little Sister Private Build Cedar of Lebanon Guitar". B&G Guitars. Retrieved 2024-12-06.
  4. guitarfromspain (2020-11-19). "The history of the flamenco guitar". Guitar From Spain. Retrieved 2025-07-07.
  5. Bouquet, Jonathan Santa Maria (2010-04-01). "The Lute - The Metropolitan Museum of Art". www.metmuseum.org. Retrieved 2025-07-07.
  6. The Acoustic Guitar Guide, p63
  7. Gordon, Gary (2024-09-01). "What Are Pianos Made Of?". Riverton Piano Blog. Retrieved 2025-07-07.
  8. "Music to your ears: CITES CoP18 moves towards strengthened regulations for tropical trees, as well as cautions exemptions for rosewood musical instruments". CITES.
  9. Case, Laura (2019-08-21). "Ebony: Leaf it as is or branch out?". The Sydney String Centre. Retrieved 2025-07-07.
  10. "Saving the Music Tree". Smithsonian Magazine. Retrieved 2017-11-07.
  11. Mottola, R.M. (20 October 2021). Building the Steel String Acoustic Guitar. Amazon Digital Services LLC - Kdp. ISBN   978-1-7341256-1-0.
  12. Strandberg, Ola (2018-05-23). "Wood Species and Electric Guitars". .strandberg* Guitars Rest of World. Retrieved 2025-07-07.
  13. Gore / Gilet (2016). Contemporary Acoustic Guitar Design and Build. Australia: Trevor Gore. pp. 4–50. ISBN   978-0-9871174-2-7.
  14. "Average Dried Weight | The Wood Database" . Retrieved 2022-03-13.
  15. "The Wood Database". The Wood Database.
  16. "Wood Handbook: Chapter 5: Mechanical Properties of Wood" (PDF). Forest Product Laboratory. 2021.
  17. "Dimension Shrinkage". The Wood Database.
  18. Wegst, Ulrike (October 2006). "Wood for Sound". American Journal of Botany. 93 (10): 1439–1448. doi:10.3732/ajb.93.10.1439. PMID   21642091.
  19. Gore, Trevor (2011-05-23). Wood for Guitars . Proceedings of Meetings on Acoustics. Vol. 12. p. 035001. doi:10.1121/1.3610500.
  20. "Acoustic Guitar Central: Recycled Tonewoods". Michelettiguitars.com. Retrieved 2016-11-05.
  21. "Adrian Lucas. Luthier Interview. MP3. | Guitarbench Magazine". Guitarbench.com. 2009-02-10. Retrieved 2016-11-05.
  22. "The Lucky Strike Redwood. Tonewood profile. | Guitarbench Magazine". Guitarbench.com. 2009-11-04. Retrieved 2016-11-05.
  23. See article posted by National Public Radio: , as well as the web site of Ciresa, a tonewood company based in the Fiemme Valley.
  24. "Tonewood in the Making". Archived from the original on 2011-05-03. Retrieved 2011-04-12.
  25. "ThermoWood Handbook" (PDF). International ThermoWood Association.
  26. "Comparison of different techniques of thermal modification, regarding the improvement of acoustical properties of resonant soundboard material Scientific Report by order of Pacific Rim Tonewoods Inc". ResearchGate. Retrieved 2021-08-16.