Rise and fall of iconic guitar tonewoods and evaluation of alternative species

Abstract

The future use of traditional tonewoods in the art of lutherie is at a critical juncture. The over-utilization of tropical hardwoods is forcing guitar makers to consider suitable substitutions for the wood species that have become iconic for concert quality instruments. The historical evolution of material selection was examined to determine how and why certain woods became de facto in the art of lutherie. Objective testing methods were designed to quantify the properties essential to material selection and provide a benchmark to compare potential substitutes. Different wood species were subsequently tested to determine their suitability for substitution. A blind test was carried out to demonstrate the indistinguishability of guitars made from different woods having similar physical and vibrational characteristics. The results indicate that a specific wood sample's physical and vibrational characteristics are more important than the wood’s identity. This thesis explores the historical development of the guitar in terms of the evolution of the iconic woods preferred for use in concert quality instruments. With the potential loss of access to these woods due to overutilization and subsequent international trade restrictions, the research goes on to define their physical and vibrational qualities to establish benchmarks by which alternative species can be measured. The objective testing methods devised in the research are based on the traditional subjective methods used for centuries by luthiers to ascertain wood quality. In addition, the testing methods were designed so that they could be easily replicated by other luthiers. Finally, four guitars were made by the author in an identical fashion except for their back and sides. Two of the guitars were made from a threatened resource, Indian rosewood, while the other two instruments were made from a currently sustainable resource, African padauk. The woods selected were matched as closely as possible in terms of their physical and vibrational properties. The test determined that instruments made from wood with nearly identical physical and vibrational properties are indistinguishable in a blind performance test by experienced guitarists.