Changing tune: Composite materials for musical instruments

Materials World magazine
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1 Sep 2016

Musical instruments are ever-evolving objects. Even today, weird and wonderful instruments made from a variety of different materials emerge each year. From theremins to earth organs, the world of musical instruments is hard to keep up with. 

The origin of the first instrument is unclear, with the discovery of a Chinese flute between 7,000 and 9,000 years old being the most definitive example of an ancient musical instrument. The materials that instruments are made of have historically depended upon what was readily available. Many instruments were made of perishable materials, such as animal skins, while others, such as flutes, were made of bone and therefore lasted longer. The flute is now more commonly constructed from silver, while stringed instruments typically use various woods to project a variety of sounds.

Composite materials have over the past decade begun to find their way musical instruments, particularly those with a large market, such as guitars. With concerns over deforestation and the wasting of wood, many companies are now forced to look outside traditional construction and seek new ways to produce their products. The needs of the musician have also bolstered this change, with increasingly vigorous touring schedules of professional artists taking a toll on their tools – sometimes dealing more pressure than traditional materials can handle.

Carbon chords

Since the late 1970s, carbon fibre and carbon fibre-reinforced polymer have made it into the global market in various fashions. By 2000, the material, a combination of carbon fibre strands and plastic resin, had applications for highly sophisticated machine parts in Europe, and was becoming an important composite material. Carbon fibre can also be used to make composites with other materials such as glass, aluminium and aramid.

Perhaps unsurprisingly, carbon fibre has also become a viable alternative to wood for many stringed instruments. One such example comes from the USA guitar manufacturer Rainsong. Formed in the 1990s by Dr John Decker, an aeronautical engineer from Hawaii, Rainsong claims to have made the first advance in guitar making material since the use of wood nearly 400 years ago with its all graphite/carbon fibre acoustic guitars. After a rained out wedding in Maui brought a halt to the musical accompaniment, Decker wanted to create a guitar that could stand up to the elements, while competing with the tonal quality of the classic wood-based acoustic.  

Rainsong claims that its guitars give a more ‘complete’ sound than traditional wooden alternatives, because of a consistent dampening effect that allows high and low frequencies to resonate on a level plane, making the higher notes less muddy. Using a patented construction technique, Performance Shape Casting, Rainsong necks and fretboards are cast simultaneously in a single graphite matrix. Holding true to the original goal, Decker claims his creations can face any weather, with graphite’s famed strength ensuring the instrument does not warp in hot or wet conditions as wooden instruments do, therefore maintaining tuning and taking a beating with relative ease. 

Carbon fibre and graphite guitars are becoming more common, with Composite Guitars, USA, showcasing its new travel-sized edition, Cargo, at the 2016 National Association of Music Merchants show – NAMM. The instrument is made in a single mould, so there are no gaps in the construction apart from the offset sound hole.

This trend continues in more specialised areas. In 2015, Nageli Swiss AG developed a trumpet bell made from carbon fibre-reinforced plastic. Nageli claimed that its design allowed for a measurable and noticeable decrease in blowing energy required for playing the trumpet. Using resin transfer moulding technology, dry fibres in the form of braided tapes are preformed and put into a mould, before resin is injected into the closed and heated mould at high pressure, as a vacuum is applied. Following a curing cycle, the bell is demoulded. To ensure the surface of the trumpet bell meets the high-quality finish required on the inner side as well as the outside, the viscosity behaviour of the resin system must be suitable for injection at high temperature. The trumpet, called the daCarbo, is now being manufactured in Switzerland.

The stiffness of the instrument panel, coupled with the damping properties of the composite materials, resulted in the reduction of non-audible vibrations of the bell and the subsequent increase in the reflection component of the sound. The geometry of the bell is designed to create a clear tone, and the production process is largely automated to deliver a consistent level of quality, while bypassing the corrosion and condensation issues of traditional brass instruments. 

Nature in music

Harking back to early instruments made from animal skins and bone, innovations in composite materials for musical instruments have also come from nature. One such material is Ekoa, a composite of flax linen and a bio-resin made from industrial waste, also described as solid linen. Initially developed by Blackbird Guitars, USA, as a 10-year project, Ekoa is designed to be an alternative to wood that looks and sounds as a wooden instrument would. Producing carbon fibre guitars such as the original Rider guitar, Blackbird founder Joe Luttwak noticed a trend in feedback for the carbon fibre model. Luttwak mentioned in a recent article that customers often complained that the Rider did not look like wood, despite its durability and sound. This led to the development of Ekoa.

Blackbird first used Ekoa to make its Clara Concert Ukulele, launched in late 2013 to much acclaim. Its latest creation is the El Capitan, a handmade and entirely composite-constructed acoustic guitar. Built in San Francisco, USA, the El Capitan is uniquely constructed using a mould to create a one-piece hollow body and neck. To do this, each mould is filled with 100 pieces of Ekoa, and cured under high temperatures before being preserved for several hours. Once the mould is set, the soundboard is bonded to the body along with the composite fretboard. The soundboard is constructed with a slight bowl to improve strength and rigidity, as well as providing a resonant projecting surface. 

Blackbird claims that using Ekoa produces a bigger sounding guitar that is durable, weather resistant, and lighter than carbon fibre alternatives. Ekoa is mass-produced by Lingrove, USA – a company formed in 2014 by Luttwak and Desi Banatao of Entropy to develop and produce the material.

Resonance in string instruments is essential for the overall sound and quality, and is often a key thought in the development of a material or instrument. Spider silk is a naturally resonant material, used to alert the spider of the presence of prey in its web by vibrating and resonating with movement. Taking this property, Luca Alessandrini, a postgraduate from the Dyson School of Design Engineering at Imperial College London, UK, has recently applied the silk’s resonance to the structure of a violin.

Alessandrini's violin is made of a composite material combining silk and resin, with three strands of golden silk spun by the Australian golden orb spider embedded in the top side. The strands and the composite casing work together to emit sound, with the spider silk vibrating the casing as the strings are bowed or plucked. The combination of fibres present in Alessandrini’s violin allows for some fine-tuning of the instrument. By altering the method of mixing the fibres it is possible to engineer the propagation velocity of the composite material, allowing it to be customised to emit a desired sound. The composite also has potential to be used in the manufacturing of speakers, amplifiers and headphones because of its customisable acoustics.

Why plastic?

If told that a certain instrument was made of plastic, most musicians would assume, in many cases correctly, that it was cheap and of low quality. Arrays of novelty instruments have ingrained this perception into the minds of many. There could, however, be a place for plastic in musical instruments – and not just for toys.

Like most instruments, flutes suffer from expanding and warping of the materials caused by changes in weather, compromising tuning and requiring greater maintenance. Founder of Taiwanese flute manufacturer The Guo Musical Instruments Company, Geoffrey Guo, began experimenting with alternative materials and designs for flutes in 2004. These experiments resulted in the Executor headjoint – the most acoustical element of the flute, where the player blows to produce sound – constructed with a composite material of fibreglass and industrial plastic called Grenaditte. The name serves the purpose of linking the composite to Grenadilla wood (dalbergia melanoxylan), with which it shares many properties such as density, acoustics, and colour. Where Grenaditte excels is in its immunity to temperature change and light weight, as well as being ideally suited for production methods employing the intricate design. Following the Executor, Guo produced an entire flute made of Grenaditte designed to combine the qualities of the early conical flute with a modern silver flute, bringing the conical tone and feel together with the responsive dynamics of the modern flute. Guo has also worked with engineered high polymer plastics for his more affordable instrument, the New Voice flute. 

The Quadrant Group has recently turned its attention to guitar nuts. Commonly made of bone, metal, graphite and even ivory on older examples, the nut is a notched strip attached at the end of the fret board on the cusp of the headstock. This insignificant looking piece of hardware not only keeps the strings in the correct position, but also has an important role to play in the tremolo system, if one is present, by providing tuning stability. 

The nut is a piece of hardware frequently experimented with by guitar manufacturers. Quadrant has worked with Raygun Guitars, USA, to use an A grade of Techtron-brand High Pressure & Velocity (HPV) PPS to manufacture high quality nuts. The material is self-lubricating, chemical- and hydrolysis-resistant and has good dimensional stability and electrical insulating/dielectric properties. 

Pick and paper

While plastic may seem an odd choice of material, the use of paper is likely to confuse many more. Gibson Guitars, USA, has for the past two-decades looked for an alternative to the increasingly rare wood ebony, commonly used to make fret boards for guitars.

Their solution is a paper and phenolic resin composite material called Richlite, created by stacking sheets of paper and saturating them in resin, before applying heat and pressure. Dating back to 1943, when it was used to make drop boxes for the US military, its waterproof and durable surface allowed Richlite to withstand drops from supply planes, along with adverse weather conditions. Since then, the material has been used by Boeing Airlines, as well as becoming a popular option for interior and exterior architectural surfaces and furniture.

In 2012, Gibson began to use Richlite on its Les Paul Custom production model guitar instead of the traditional ebony. Gibson claims that Richlite is actually superior to ebony as the quality is consistently high, and no material is wasted searching for supposedly ‘good’ ebony, based on grain and colouring. Of course, there are those who dislike the new material for its different feel and look, but this has not stopped Gibson from now using Richlite as standard on its Les Paul Customs. 

Moving away from high-end guitar manufacturers to a novel product making use of cardboard, the Corrulute is an interesting take on the classic lute, and gives an insight into the construction of stringed instruments. Corrulute, UK, is a small company run by Richard Barry and Neil Turner. The Corrulute itself is a ‘make it, play it’ instrument, sold as a build-it-yourself kit, and originally marketed to children – although adults quickly latched on, too. Simple in its construction and use of materials – cardboard, plastic and wood – the product introduces people to the world of stringed instruments and their construction. At the simpler end of the composite instruments mentioned, it is an example that sometimes, less is more. 

The use of composite materials in musical instruments certainly has benefits for the musician, the manufacturer, and the environment. Guitar manufacturers are leading the way with the implementation of such materials into their products. As guitars are on the cheaper end of the manufacturing scale, they are more widely available at lower prices, which could help to increase the awareness to the benefits of composites materials. In some cases, particularly for those instruments that are heavily reliant on wood, new materials may prove necessary if they are to be made for many years to come. 

To see how the El Capitan is made, take a look at the video on the Materials World app.