The Materials Science and Sustainability of Tonewoods for Manufacture of Stringed Musical Instruments

The musical instrument manufacturing industry relies on a particular natural resource: tonewoods. Tonewoods are woods that exhibit the best combinations of mechanical, chemical and physical properties to produce the most harmonious, playable, durable and beautiful instruments. Acoustic properties of significance are density and modulus, but other properties are also important—strength, because a fully tensioned guitar must sustain nearly 200 lbs of tension; dimensional stability, because musical instruments must exhibit minimal dimensional change due to environmental moisture and temperature; and fabricability. Other properties, such as wear, chemical and ultraviolet light degradation resistance matter for durability. Finally, the fineness and uniformity of the wood cellular structure impact acoustic properties, such as sound velocity, resonance and damping characteristics. Tight, consistent wood grain is key to all these properties, and these must have appropriate growing conditions.

Common tree species from which modern guitars have been fabricated are: spruce and cedar (tops), rosewood and mahogany (bodies), and ebony (fretboards). There are particular species that are considered the optimal, for example, Adirondack spruce (Picea Rubens) and Brazilian Mahogany (Swietenia Macrophylla)—both have been over-harvested and the latter is regulated per the Convention on Trade in Endangered Species (CITES) as a species in need of strict regulation to prevent extinction. Because of these challenges, major guitar manufacturers have developed sustainable sourcing plans, and are heavily invested in identifying, producing and marketing more renewable wood substitutes for traditional instrument applications.

In this presentation, we will discuss the history and principles of materials selection for stringed instrument construction, how wood microstructure affects musicality, and explore what the instrument manufacturers are doing to address supply limitations. We will also discuss how engineering materials selection methodologies can guide the identification and development of substitutes that are more available and affordable while having a smaller environmental impact than traditional materials.