A person who is specialized in the making of stringed instruments such as guitars, lutes and violins is called a luthier.
Skills
In general one can distinguish three main aspects of guitar making: "Sound" feature that includes shaping the wood (vibrational aspects: densities, stiffness), wood-selection, shaping the bracing; to design; etc. The goal aim is a sound quality that helps the musician create music. Guitars by different builders often reflect different sound preferences—e.g., when comparing instruments of Lacôte or Grobert, with Torres, etc. All can have high sound quality, yet multiple guitarists feel one may be more appropriate for particular repertoire choices, e.g., Lacôte or Grobert for "classical era repertoire" or "central European romantic repertoire"; versus Torres for "Spanish or late-romantic nationalist repertoire", etc.). "Playability" aspectsThis includes the shaping of the frets,Fernandez "Custom Set-up" for frets, etc.; video demonstration string-spacing, neck-width, neck, nut and bridge height (influence on action); decisions about scale-length; etc.The aim is a guitar that is easy and comfortable to play, does not have string-buzz, and suits the requirements/desires of a particular player. "Visual/decorative" aspectsThis includes the visual features of the guitar, including rosette design, inlays, ornamentation, etc. (In general these creative visual aspects should not interfere or diminish the sound features, or hinder the playability of the guitar).
Fernando Sor has written that an instrument-maker "should be an accurate draughtsman, understand the common principles of mechanics, the composition and resolution of forces, and the laws of vibrating strings and surfaces".
Shaping of wood with acoustics and resonance aims This shaping of the wood is known as "resonance plate tuning"Die Theorie der harmonischen Abstimmung der Resonanzplatten bei der Geige ... (1907) by Max Grossmann (Grossmann's text should not be interpreted as the only way to do plate tuning. They simply represent Grossmann's own theories—which were used by luthier Otto Seifert from c. 1904 - c. 1914) (or "plate tuning"). It refers to a comprehensive tuning of the wood and bracing (its density, thickness, tension, sound-influence) to influence the acoustic properties. It does not refer to a tuning of the guitar-body to a single "default" frequency. Instead, it is a comprehensive way of shaping the wood and its response and resonance properties to improve the guitar's sound. The "tuning" of the wood is also called "voicing" the instrument. The techniques used trace to previous centuries, especially in violin-making (example: attempt at understanding some of the tuning schemes of Italian violins: 1 , 2).
Some guitarmakers believe that the actual voicing of the wood, and working with and "shaping" the wood (during and even after construction) is more important than the outer construction itself (such as chosen bracing): "As my skill and experience have grown I have come to believe that what makes a good guitar good is firstly how well fine tuned and balanced it is rather than what type of strutting system it is built with. Different strutting systems can add different flavours to the sound but is never the main factor in the Good Guitar." (Per Hallgren)
Sound characteristics (Timbre)
Spectrum One of the important aspects that good luthiers need to understand, is that a single tone consists of the "fundamental and simultaneous overtones".Modes, Overtones and Harmonics - Chapter 3 from The Physics of Music and Musical Instruments by David Lapp (Historically the scientific analysis of this discovery can be associated with Nicole Oresme,Nicole Oresme Marin Mersenne and Joseph Sauveur.) The ratio of the "intensity of fundamental" and the various overtones, defines the "colour" (Frequency spectrum) of the tone. Overtones are simply frequencies that are at a multiple of the base fundamental frequency. (Overtones defining colour, do not only occur in instruments, but also in the human voice. When singing a note, there are multiple overtones present. Singers experienced in overtone singing are able to control their voice in such a way, that they can increase the intensity of any high overtone to such an extent, that it becomes clearly audible, whilst simultaneously singing the fundamental. In this way two pitches (fundamental and high-intensity overtone) can be made clearly audible while singing.Overtone singing, Frequency Spectrum of the voice, showing the fundamental and various overtones: octave, ..., and high-intensity higher overtones (a melody is created, by shifting the intensity to various overtones, while others are more suppressed))
Tonal colour is an important characteristic on a guitar. Usually the notes of the guitar's different registers (low bass, mid-range, high, etc.) have different colour-spectrums, i.e., differing relative intensities of fundamental to different overtones.
Various types of guitars have tone-differences in the various registers (also differences in response, action, etc.). Specific colour-spectrum characteristics of certain types of guitars can be said to form a specific "sound aesthetic"—this is like a "fingerprint" of the characteristic of that type of guitar. Other guitars have a different "sound aesthetic", i.e., a different colour-spectrum characteristic. Different historic instruments reflect various sound aesthetics.
Temporal change of spectrum (attack/onset, decay) Important in characterizing the sound of instruments (or more precisely, notes of particular registers), is how the player initiates the sound. This is the attack or onset: a short-duration transient. This occurs at the moment when a string is plucked - the string builds up motion for some time, before it can vibrate in the normal way. The attack is nonlinear and usually has high-pitched frequencies present. The duration of the transient (until normal string vibration continues) and frequencies occurring during the transient, are an important factor in how we perceive the tone.
Once the string is in its normal mode of vibration, the standard colour-spectrum is present. As time progresses the amplitude of the vibrations decreases, and usually the intensities of higher pitched overtones decay at a faster rate than the intensities of fundamental and lower overtones (thus a change of colour over the vibrating-time).
In this way one can observe the acoustic "envelope": the attack, followed by the way the intensity of frequencies (fundamental and overtones) decrease with time. The "envelope" can thus be regarded as the temporal change of the spectrum of the sound. This envelope is different for notes in different registers.
Thus the tone or timbre is determined by: Attack or onset (how long until normal vibration of the string? -> response of the guitar) Relative intensities of frequency spectrum: fundamental to overtones (defines colour -> colour change over vibrating time, since the higher-freq overtones decay quicker)
These factors can be influenced by the shaping of the wood. A good luthier understands how to shape the wood to directly influence these acoustic properties.
Guitar players can actively vary the timbre by the way they pluck the string—by changing the nail or finger angle, the distance from the bridge, etc. A good instrument helps the musician produce widely varying timbres and have yet have good resonance. Nevertheless, a default colour and response is identifiable for notes in the different registers and define the instrument's sound.
Styles of "sound aesthetic" As was mentioned, it is possible to group historic instruments according to the colour and response sound characteristic (present for notes in the various registers). A baroque guitar has a different "sound aesthetic" than a 19th-century guitar, i.e. a differing colour-spectrum in the various registers (low, mid, high) and a different duration of attack (response of the instrument).
The "sound aesthetic" is determined by the sound characteristic of notes in specific registers (an instrument's low notes has a different relative timbre, than its high notes).
There is a historical parallel between musical styles (baroque, classical, romantic, Spanish nationalist, flamenco, jazz) and the style of "sound aesthetic" of the musical instruments used: Robert de Visée played on a baroque guitar with a different sound aesthetic than the guitars used by Mauro Giuliani or Luigi Legnani - they used 19th-century guitars.
Whilst the difference between baroque guitars and 19th-century guitars is large and immediately obvious, one can also identify differences in style within the 19th-century guitars themselves: They are part of the same family, but one can distinguish early Italian instruments (Fabricatore), then French instruments and Viennese instruments, etc.As an example: Viennese guitars usually have more fundamental in the tone (but less, than with Torres fan-bracing), while the earlier French models have more overtones
Guitar making in the 19th century To get a picture some of the ideas on guitar-building from the 19th century, some newspaper reports of guitar-related patents (note that the newspaper reports given in the cross-references are only brief mentionings, with the actual patent papers providing more details and drawings etc.) and other newspaper writings are listed:
Arzberger Johann Georg Staufer and Johann Ertl1 Bernhard Enzensperger Franz Besetzny Wenzel Soukup Lacôte, Carulli: Décacorde J.F. Salomon: Harpolyre Ventura: Harp Ventura (modification of harp and guitar)
There are also 19th-century mentionings of Lacôte winning a prize for the quality of his instrument - the second prize went to Laprevotte. In the competition organized by Makaroff, it was the guitar of Scherzer that took first place.
Guitars in the 19th century were initially all ladder-braced Examples of ladder-bracing:1828 Lacote, A. Stauffer & Comp., ca. 1825, Lavigne, Paris circa 1815, (Pons-style Y-Bracing) (ref)FabricatoreStauffer guitar from about 1836 (ref)Early 6-string guitar from about 1780: 1 , 2 , 3 , 4 , 5 (ref )Nicolas Bonafon around 1840 (ref) and had their tonal energy spread over a lot of overtones (a desirable characteristic in instruments of the early classical and romantic era), as opposed to the more fundamental-rich guitars of Torres. Francisco Sanguino was one of the first to experiment with fan-bracing, then came Páges and Panormo—but Torres did not use it, so Panormo and Páges still had more tonal energy spread over overtones, compared to the Torres guitars, which focus tonal energy more in the fundamental (desirable in Spanish music).
Movable frets To solve all guitar intonation problems, or help guitarists use different musical temperaments (or to play microtonal music) it is necessary for the frets on the guitar to be adjustable. Work in this field began in the 19th century, when Thomas Perronet Thompson (1783–1869) wrote a work on the Enharmonic Guitar,Instructions to my daughter for playing on the enharmonic guitar: an attempt to effect the execution of correct harmony, on principles analogous to those of the ancient enharmonic by Thomas Perronet Thompson (1783–1869)image Review (The Harmonicon, 1830) Excerpt on temperament (The Harmonicon, 1830) Extended Review (The Westminster Review, Volume XVI, 1832) with ideas used by Panormo.Louis Panormo, "Enharmonic Guitar", London 1829 Lacôte also built a "guitare enharmonique"Lacote: Guitare Enharmonique (E.1043 Cite de la musique) photo1 photo2 ref "An enharmonic guitar by René François Lacôte, Paris, ca. 1850"; Description & Restoration Report: Ian Watchorn, Melbourne, 1990. with movable frets.