Strings/Intonation/Action/Tuning

Guitar Strings

The six strings of the classical guitar are numbered S1-S6, in standard tuning from high to low: EBGDAE. The guitar is a transposing instrument; the instrument sounds an octave lower than the written music.

Each string provides vibration that drives the tone wood, consisting of a fundamental frequency and all its harmonics. The tone woods can filter, shape, and amplify the resulting sounds, but if the string didn’t create a given harmonic, the guitar body, being a passive resonator, cannot generally add it or increase its power beyond the relative filtering actions of the resonant wood chamber. This explains the critical importance of strings to an individual instrument’s sound. The woods, construction techniques, and string qualities work together to create a guitar’s timbre. For a given instrument, the string characteristics are the only variable.

Strings were originally gut. After WWII, string technology jumped ahead with the invention of nylon. At the start of the 21st century, new polymer and composite (carbon fiber) technology may be poised to create yet another string revolution. Mixing strings with different tensions, and from different manufacturers, is frequently done to perfect an instrument’s sound.

Strings are normally replaced one at a time, S1->S6, the wisdom being that avoiding dramatic tension changes is easier on the instrument. Wound strings usually come with one end loosely wound for added flexibility. I find this end easiest to maneuver at the head tuning peg, where strength is less important. Standard practice is to thread strings over the tuning pegs; thus counter-clockwise turns of the peg increase tension on the bass strings and clockwise turns increase treble string tension. Other common recommendations with no seeming relevance to a better-tuned guitar are to pre-stretch the strings; use only 2-3 turns around the tuning pegs; do not allow individual windings on a peg to cross over each other.

Anchoring strings at the bridge tie-block can be done in a variety of ways. A simple knot at the bottom of the tie-block may do, although the result can look less than professional. The usual method is to feed the bridge-end of the string through the tie-block hole from the bottom, then loop back over itself, pinching the stub end under the string loop at the bottom of the tie block. For treble strings, two or three loops over itself before the pinch is more certain to hold under tension.

Due to the slippery nature of composite strings, the conventional method can end in frustration even with three loops. But these strings are so thin that they can be looped through the bridge tie-block twice before pinching-off as above. This creates enough extra friction to hold the tuning. Another reported trick is to heat the end to make a small ball that will grab and hold within the normal tie pinch.

Guitar Scale Length

Scale length is the length of the vibrating strings, approximated as the distance between the nut and the bridge saddle, but more exactly, twice the distance from the nut to the top of the 12th fret. The canonical classical guitar scale length has been 650mm for more than a century. Virtually all classical guitars fall in the range 630-670mm.

Various parameters affect string vibration, including string material, gauge (mass per unit length), and tension. Tension is related to the gauge of the string material and the guitar’s scale length. The larger the string gauge and the longer the guitar scale, the more tension is required to reach a given pitch.

Scale length affects the tone of an instrument in complex ways, described as the ‘voice’ of the scale. The shorter the scale length, the lower the string tension, which in turn changes the harmonic structure of each string’s tone. A shorter scale also spaces the frets slightly closer. Lower tension and closer frets make an instrument easier to play for smaller hands, e.g. Señorita models typically sized at 635mm.

Longer scale length is associated with more power and projection, increased frequency response at pitch range extremes, and increased sustain. But fine guitars can be found at any scale.

Guitar Intonation

Equal Temperament (ET), the original well-tempered scale of Aristoxenus (~350 BCE), was revived in the 18th century to form the basis for subsequent western music. For fixed-tonality instruments (eg. fretted guitar, piano), ET is the best-compromise for our simple, natural 12-tone scale.

ET divides an octave into 12 equal-spaced half-tones (i.e. D#=Eb), ensuring equal consonance in all pitch ranges and keys. Compared to just tuning (string harmonic ratios), ET octaves are exact, ET fourths and fifths magically approximate just tuning (~0.2% off) on all strings at all frets, but ET thirds and sixths fall short with audible inharmonicity (~1% off). Since other temperaments (meantone, Pythagorean) emit some nasty ‘wolf’ chords limiting their utility, we learn to accept the slight dissonance of ET thirds.

Setting up a guitar to be in tune with itself and with our ears is an intricate problem. The luthier sets frets at ET intervals relative to nut and bridge (2nd fret sometimes fudged). But when fretting a string, it is stretched, placing it under more tension, and hence playing sharp relative to its tuned open tone. The luthier can negate the potential intonation difference of an open vs fretted string by making slight, string-dependent adjustments to bridge saddle and nut positions (~1mm; ~0.3mm). The resonance frequency of the guitar body can also affect apparent intonation accuracy.

Guitar Tunings

Of the thousands of possible tunings, we use a standard tuning that dates from the Renaissance, replicating the tuning of 16th century 5-course guitarra on S1-S5, and adding a low E string to complete a full 2 octaves. Standard tuning is mostly in fourths from low E to the E two octaves above (EADGBE). The exception interval S3 to S2 is a major third.

This standard tuning aids playing: simpler fingerings, minimized left hand movement, easily learned note symmetries. The standard guitar tuning is related to that of the high six strings of the renaissance lute. To play lute music from tablature on the guitar, tune S3 down a half tone to F#, then place a capo at fret three (up a minor third).

Many alternative tunings are used today. A good example is guitarist/songwriter/performer Joni Mitchell, who uses a different tuning for each song (only slight exaggeration), and who avoids standard tuning. The attractions of alternate tunings: make certain notes and chords more available to the performer; allow more notes to fall on open (non-fretted) strings to enhance tone/harmonics; facilitate a certain type of playing style (slack key, slide, blues); extend the range of the guitar; or match a vocal range. Perhaps the most common alternatives are drop-D and double-drop-D tuning, which lower S6 one tone to D (and S1 in double), useful for music in keys of G and D.

Several open tunings are used for easy blues guitar, each named for the major chord resulting from all six unfretted strings being strummed. See the article: Open Tuning Tutorial. DADGAD is widely used in many keys, characterized by the major second between S3 and S2. It is open-D tuning, except with S3 raised a half tone, from F# to G. Crafty tuning is a current attempt to redefine the standard tuning in fifths, CGDAEG, increasing the range of the guitar. This is similar to the all fifths tuning of the violin, except S1 is tuned to G, not the B above.

Tuning is done from flat to sharp, dictated by the mechanics of the tuning pegs. If sharp initially, flatten first before precise tuning. A tuned piano, or digital tuner such as the Korg TM-40, can provide a reference for each string tone. The TM-40 can also improve the ET thirds tuning, when a performance would benefit. Or use a standard A pitch fork to tune S6 at the fifth fret and finish with one of the next methods.

A method using octave string harmonics can place a guitar in standard tune (only octave harmonics match ET tuning). First get the two open E tones and the fretted E in unison. Tune S6 to a frequency reference, tune open S1 to the 5th fret harmonic of S6, and tune the fretted S4 E to the 12th fret harmonic of S6. Tune the Ds on S2 (fretted) and on S3 to the 12th fret harmonic of S4. Check for unison of the 12th fret harmonic on S3 with the G on S1. Finally, tune the 12th fret harmonic of S5 to the A on S3.

A more general tuning method can tune the guitar to any tuning, although it allows tuning errors to propagate. First tune S6 to a reference tone, then tune the other strings sequentially by fretting the prior tuned string to produce the higher pitch of the next string to be tuned. (If the open high and low strings aren’t then in tune, repeat the tuning.) An alternate tuning nomenclature based on this tuning method specifies the S6 note and the frets used to tune the pitch of the subsequent strings (rather than the note played by each open string). Thus, for drop-D tuning, DADGBE becomes D75545.

Guitar Action

The action of a guitar refers to the distance between the strings and the frets. The higher the action, the fewer the buzzing tendencies, the greater the playing effort, the slower the response. So ideally, one wants the lowest action for which a given string tension will be able deliver clean results. But there is no need to finesse the action to its lowest possible height on a classical guitar, unless ultimate speed is the objective.

Action varies along the neck, getting wider at higher frets since string motion amplitude is highest in the middle. Guitar designs will also give higher action on the base strings to account for their greater vibration amplitude. Medium classical action typically is specified as: fret1, S1 0.6mm, S6 0.8mm; fret 12, S1 3.2mm; S6 4.0mm.
(Note: penny+nickel~3.2mm and penny+dime+penny~4mm.)

Given a true neck, action adjustments involve raising or lowering the bridge saddle and/or the nut. My guitar came with a low action, ~70% of medium specification above. There is no audible fret noise on open strings when played at my maximum intensity.

Guitar String Choices

Decades ago, a teacher suggested pairing La Bella black nylon treble strings and Savarez wound bass strings. This combination served well for folk guitar on my first guitar and I saw no need for further experimentation. A new appreciation for the importance of strings to the sound quality of a guitar, combined with the advent of composite strings, the acquisition of the new guitar, and a venture into classical guitar music, all argue for listening to the effects of different string types.

Another piece of guitar wisdom picked up along the way suggests amateurs will do well by choosing strings with as low a tension as possible, as long as the strings do not become sloppy with excess vibration. Medium tension provides a good balance of controlled tone and easy play. Higher tension may be used for strings with lower tunings than the standard for which the string is rated. Also a higher tension S4 may eliminate a tendency of G-strings to have a ‘tubby’ sound not matching the timbres of the other string harmonics.

My new guitar arrived from fleaBay with nylon strings of unknown make and vintage. New strings were the first imperative to form a true impression of the sound. I decided to go for the carbon with a Savarez Corum Alliance 500AR set, but soon decided the trebles didn’t work. The carbon S1 was very thin and played flat when fretted at 12, relative to the open S1 octave harmonic. S1 has a musical tone when played open and soft, but fretting and loud play robs it of life, resulting in a tinny, strained tone.

The intonation of the other strings was acceptable. S3 seems relatively less musical. For the bass strings, S6 in drop-D tuning is a little loose; a high tension S6 seems a worthwhile future experiment. The power, noteworthy sustain, and rich harmonics of the Corum bass strings seem to excite the tonewoods to good advantage. Guitar Salon concurs about the Corum red basses: rich and warm, excellent projection, good longevity, reliable intonation, plenty of color variety and flexibility for vibrato. Bass strings are keepers.

Moving on, I bought a set of Hannabach Goldin composite trebles to go with the Savarez Corum basses. These are medium-high tension (they don’t come softer). The Goldins impress me as a more musical set than the Savarez carbon trebles on my guitar. Intonation seems right on when comparing fretted string with its octave harmonic, although the S1 sustain drifts sharp by over 10 cents. The timbre of S1 and S2 is consistent, tending to bright rather than mellow, but songful nonetheless. The S3 timbre is less bright, but the sustain surprisingly matches or betters that of S2, which keeps it out of typical S3 ‘tubby’ land.

The Hannabach’s are suprisingly easy to play with my guitar’s low action. Their long sustain and brightness allows them to hold their own with the Corum basses in a nice balance. Mine is not a powerful guitar, but this string combination has some punch and liveliness, the trebles allowing the bright tendencies of the tone-woods to be heard. This combined set of strings invites playing for a while to reveal the promised crisp sound of the K5’s cedar on koa.

Observation: The guitar’s tone was getting trashed randomly for reasons that puzzled me. What was going on with these new carbon strings? Then in an awesome flash of inspiration, I deduced it resulted from turning on a ceiling fan, creating a beating interference with the sound hole string resonance. Research later confirmed guitars are generally ‘allergic’ to fans. Who knew?

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