More than you ever wanted
to know about strings – Part 1
Strings are the heart and soul of the acoustic guitar and indeed of
any stringed instrument. All the rest of the instrument does is make
the sound of the strings louder and allow the musician to select and
sound different notes.
Strings may seem like such simple objects, but it has taken thousands
of years of technological development to produce the musical strings
of today and the development and design characteristics of stringed
instruments have been determined entirely by the type, limitations and
quality of the strings available at any given time.
Strings and stringed instruments seem to have started their development
with the bow. As far as we know, the first bows appeared in the late
Palaeolithic or early Mesolithic. The earliest evidence for bows in
Europe comes from Stellmoor in the Ahrensburg valley north of Hamburg,
Germany and dates from the late Palaeolithic Hamburgian culture (9000-8000
BC). Although it’s often assumed that the bow was first developed
for hunting and perhaps used as an impromptu musical instrument, which
then developed into stringed instruments, there is now evidence that
things may have developed the other way around and that the earliest
bows were crude musical instruments.
Bowstrings have been made of a range of natural materials, such as
plant fibres and animal sinew. Most Neolithic bows are made of yew,
a material that was later commonly used for the ribs of lute bowls.
Ötzi the Iceman found in the Ötztaler Alps carried an unfinished
yew longbow, with a bowstring of nettle or flax fibre.
The myth of catgut strings
Although gut strings have been found in the tombs of the pharaohs, gut
string making as a European industry didn’t get started until the
early 14th century. Gut guitar and violin strings remained in general
use right up until 1946.
There is a common misconception that gut strings are made of catgut
and at least two explanations of how this myth got started. One story
has it that the early string makers borrowed a technique from rope makers
for twisting strips of sheep gut together to make the thicker string
gauges. The rope makers used this method to make the thinner cords for
ships rigging and the nautical term for these cords was ‘catlines’.
Another story is that back in 1300 AD the town of Salle in Pescara,
Italy, was famous for saddle making, partly because the saddles were
stitched together using a strong thread made from the intestines of
the local mountain sheep. Tradition credits a man called Erasmo for
first thinking of using the thread for strings. Erasmo was later sainted
for starting an industry that became very important for the town and
Saint Erasmo is now, not only the town’s saint, but the patron
saint of string makers.
When people asked about the secrets of the fine musical strings made
by the string makers of Salle they were told by the townsfolk that the
strings were made from catgut. The string makers thought they would
protect their trade by circulating this story because, at the time,
cats were regarded with a great deal of superstition and it was believed
to be extremely bad luck to kill a cat.
Two of today’s string companies, D’Addario and E. Mori (LaBella
strings), both now located in the USA, are proud to trace their history
all the way back to their family business in the 14th century town of
The history of metal strings
Wire is made by starting off with a thick bar of metal and then drawing
the metal through conical holes in a series of progressively smaller
‘dies’ to make wire of different diameters. This process
goes back to around 400 A.D. The earliest currently known die plate
is one discovered in Viking Scandinavia that has been dated sometime
between 500 and 700 A.D. Each time the metal is passed through a die
it can only be reduced by a certain amount or it will snap. This is
the origin of the various wire gauges and string making has its own
gauge standard of Music Wire Gauge or M.W.G.
Early metal strings, for example harp strings, were made, either from
single wires, or rope-twisted strands of gold, brass or iron. This placed
restrictions on the thickest strings that could be made and limited
the range, particularly in the bass, of any given instrument.
Wound bass strings, with a core of gut or silk, wound with silver or
silver plated copper wire, weren’t invented until around 1650
and high quality, polished steel wire, suitable for strings, became
generally available in the 1830s. Gut strings were replaced by nylon
in 1946 due to a shortage of sheep (and therefore guts) following the
Second World War.
The characteristics required of musical instrument strings
Musical instrument strings must possess quite a number of demanding
They must have sufficient tensile strength to be tensioned to the required
operating pitch and remain elastic, be uniform in diameter and density
and be unaffected by temperature and humidity. Strings need to be as
flexible as possible, resistant to friction wear and resist corrosion.
By any standard, even given the materials science of today, this is
a punishing list of requirements. Of course, real strings aren’t
perfect and only satisfy each of these requirements by varying degrees.
Tone, scale length and picking position
As stated in the introduction, the strings are the source of all the
sound that a guitar makes. The rest of the guitar may modify the quality
of that sound but it can’t add anything that isn’t already
there. The harmonic content and purity of string vibration is quite
dramatically affected by scale length. The longer a string is, the less
it is affected by its own stiffness and the wider the range of accurate
harmonics it produces when it vibrates.
To put it another way, the character of the sound a string produces
is quite dramatically affected by its length. So much of what we think
of as the sound of a guitar is a direct result of the scale length.
The characteristic ‘guitar’ sound is also affected by the
natural picking position, at about a fifth of the string length, accentuating
some harmonics and damping others.
Doubling a solid (unwound) string's diameter quadruples its strength
and the tension required for a particular pitch, but increases its stiffness
Today, after thousands of years of evolution, musical instrument strings
are made from only a few materials. The only major change in materials
in the last hundred or so years has been the substitution of nylon for
sheep gut and even then gut strings are still being made by specialist
string makers. What has changed is the quality, accuracy and consistency,
of the materials and of the manufacturing processes, to produce the
finished product. In recent years alloys have been fine tuned by the
use of small amounts of additives and by changes in manufacturing methods.
String cores are almost without exception made of tin plated Swedish
steel for metal strings and multi-strand nylon for wound nylon strings.
A relatively small range of metals are used for the wrap wire of wound
strings and acoustic strings are almost always wound with copper or
one of its alloys. Electric strings (and often Dobro strings) are wound
with harder materials like nickel, nickel plated steel or stainless
steel. Bowed instrument strings are sometimes wound with aluminium wire
and monel metal tape and flattened nylon are used to wind tape wound
strings. Silk is also used as an inner wrap on some strings to modify
Metal string construction
Musical instrument string manufacturers do not make the wire from which
metal strings are made, but buy it from specialist wire mills. For example
most string manufacturers buy at least some of their wire from the Mapes
Piano String Company in the U.S. or the German company Roslau. Wire
used for strings is known in the industry as ‘music wire’
and the wire used for the plain strings and for the cores of the wound
strings is made from high carbon steel, that is spring tempered and
often referred to as ‘Swedish steel’. Although music wire
is available un-plated, steel music wire for guitar strings is usually
tin plated to minimise rust. Other plating materials are sometimes used,
such as bronze or even gold.
Here’s a picture of a typical wire drawing machine, this one’s
made by Morgan-Koch, with the wire being drawn through successively
smaller diameter dies via a system of wheels.
A section of the wire store at Rotosound
To make plain strings (there is no difference between acoustic and electric
plains) the string maker cuts off a length of wire of suitable gauge
and twist locks a small brass cylinder, know as a ball, onto one end.
Length cutting and string ball attachment in most string factories is
a totally automated machine process. Strings for some instruments such
as the mandolin may have a simple loop twisted onto one end. Nylon guitar
strings, with their greater flexibility, are usually tied to the guitar
bridge, but recently have also been available with ball ends.
Plain steel string ball end and twist.
Wound strings start with the same process, but in addition are wound
with a suitable gauge wrap wire to create a finished string of the required
gauge. Large diameter strings may be over wound with a second layer
of wrap wire, but this is very unusual for standard acoustic guitar
gauges and is normally only found on the bass strings for baritone guitars.
Hand winding at Rotosound. The round weight on the rod gravity tensions
the core via a mechanical linkage to the string drive chuck.
Wound strings have the wrap wire applied, not surprisingly, on a string
winding machine. These vary in complexity from simple machines that
just hold the length of string core wire under tension and spin it,
while the wrap wire is fed on by hand, to machines with lead screw or
belt driven heads that feed the wrap wire on, under electronically controlled
tension. At present even the most sophisticated string winding machines
are not fully automated and require a human operator to load the cores
and unload the finished wound strings. Although it is possible to buy
complete string winding machines from a few companies that specialise
in them, many string makers are proud to design and make their own string
winding machines and say that their strings exhibit special qualities
due to the way their particular machines tension the core and the wrap
wires. Some string makers have also improved their productivity by building
machines that wind a number of strings at the same time.
A Rotosound, 2 string, automatic winder in action.
Hex cores versus round cores
The core wire used for the vast majority of modern metal-wound guitar
strings has a hexagonal cross section. This stops the wrap wire from
un-coiling when tension is released as the newly made string is removed
from the winding machine. The six points of the hexagonal wire bite
in to the inner side of the wrap wire as it is wound on and lock it
into place. However wound metal music strings weren’t always made
this way. Because of the pianos great range in pitch and dynamics, piano
design has been a rich proving ground for string technology. For example,
most wound piano strings are still wound on round cores because this
construction produces a slightly more flexible string, so harmonics
generated by round core strings differ from those generated by hex core
strings. The resultant tone, at least of round core piano strings, is
felt to be superior.
Wound piano strings also differ from guitar strings in that the wrap
wire stops just short of the bridges at either end of the string, to
minimise string stiffness. This means that piano strings have to be
custom made to fit each model of piano. Windings on these strings are
locked in place by hammering or rolling flats onto a section near either
end of the round core before winding, effectively making a short, square
cross-section of core for the last turns of the wrap wire to bite onto.
Hex core ‘universal’ replacement piano strings are made,
but only for use as quick, cheap replacement strings. The hex core construction
allows the piano technician to unwind the wrap wire to expose the core
at either end of the string, without the risk of the rest of the wrap
British string makers, Rotosound (www.rotosound.com), make both bass
and guitar strings with ‘contact cores’ that, like piano
strings, have the windings stop short to expose the core where it passes
over the bridge, although the nut/fret end of the string of course remains
A few string makers, for example Newtone in Debyshire (www.dwmee.34sp.com),
do still make round core wound guitar strings. Newtone use the piano
string technique of creating flats on the core of wound strings, near
the end of the string, to lock the windings. Even using this technique,
because of the risk of the wrap wire uncoiling and becoming loose on
the core, it’s harder to produce round core strings of consistent
quality than it is using hex cores. String consistency and stability,
throughout the industry, improved dramatically when hex cores were adopted.
Wound string tone and the wrap material
The harder the wrap wire material used, the brighter the tone of the
finished string. Stainless steel wound strings, normally only used on
electric instruments, are very bright and the availability and use of
bright sounding, stainless steel strings on the electric bass has lead
to the development of a range of new bass techniques and the adoption
of the bass guitar as a solo instrument. The shape of the winding also
has a tonal effect and a round wrap wire produces a bright string, while
tape or half-round wound strings have a warmer sound. This is because
the round wire winding, like a spring, flexes quite easily and doesnt
damp the higher frequencies. The tape winding is stiffer. Monel metal
tape, another alloy of nickel and copper, is used on most tape-wound
Silver was the first material used as a wrap wire for wound strings,
but this soon changed to silver plated copper, retaining the expensive
appearance, at lower actual cost. The silver plating was well within
the scope of available technology at the time wound strings were introduced
and it helps protect the copper against corrosion, although silver itself
also tends to tarnish in today’s polluted air. Copper is a ductile
metal that is relatively easily formed into wire and is also heavy enough
to add significant mass to the lower pitched strings.
Wound nylon strings are still wrapped with silver plated copper wire,
partly to obtain the accepted tone and partly because the soft copper
can be wrapped over the filament nylon core, without it being necessary
to apply very high tension to the core during the winding process.
Steel core, silver plated copper wound strings are available and are
usually regarded as specialist strings only used for the gypsy jazz
style and sound of Django Reinhardt. These shouldn’t be confused
with the silk and steel ‘folk’ strings that include a layer
of silk or nylon filaments between the core wire and the wrap wire,
to produce a softer, almost nylon string sound in the bass.
Brass and phosphor bronze, are alloys based on copper as the main ingredient.
Alloying elemental metals and other elements together produces metal
alloys with characteristics that don’t exist in the pure constituents.
Phosphor bronze is an alloy of copper with tin, to produce a tougher,
harder metal. Brass string wrap wire has the least copper at 80% alloyed
with 20% zinc and strings wrapped with this alloy are often misleadingly
referred to as 80/20 bronze. The relatively high percentage of zinc
gives it a light yellow-gold appearance and this harder alloy gives
the wound strings a bright sound.
Phosphor bronze is mostly copper, alloyed with between 3.5% and 10%
of tin. Alloys with slightly different proportions of the component
metals are used by different string companies. Less than 1% of phosphorus
is used in the alloy and it was originally added to remove oxygen from
the mix during melting. This softer metal wrap wire results in a string
with a mellow, warmer tone than the 80/20 brass alloy. Phosphor bronze
wound strings have a slightly red appearance compared to brass (bronze)
wound, due to the higher proportion of copper in the alloy.
Nickel wrap wire is used mainly on electric guitar strings and is normally
regarded as producing too bright a tone for use on acoustic guitars,
although nickel wound strings are used by Dobro players and some mandolin
The upper string in this picture is phosphor bronze wound and the lower
is brass wound.
A Nylon, silver-plated copper, wound string.
Wound string wrap to core
There is one ‘hidden’
parameter which string companies do have the opportunity to vary and
which may be the biggest difference between otherwise similar string
sets and that is the ratio of wrap wire diameter to core wire diameter,
of the wound strings.
Up to a point using a larger core diameter gives a string greater volume
and sustain, but string stiffness is increased, making the string harder
to play and its harmonic purity is compromised. Using a thin core results
in a more flexible string that is easier to play, with good harmonic
purity, but lower volume and sustain. Hex core dimensions for standard
string set gauges and tunings don’t normally exceed 0.016 across
the flats for the low E string. Hex cores normally increase by about
0.001 per string from the wound g string upwards, although some manufacturers
may use the same core size for two successive wound strings in a set.
String and String Set design
Designing a musical instrument
string, or even a string set, is quite a complex problem because of
the number of variables involved. There is the required pitch, material,
mass, tension and breaking strain of the string itself, but because
the string interacts with the instrument it is fitted to, factors such
as the scale length and resistance to tension of the instrument must
also be considered. In the dim and distant past the instrument and strings
would have been made by the same person, by a process of trial and error.
Today there is little interaction and guitar and string makers tend
to develop their products separately. Much of the time each takes the
others products pretty much for granted.
If you ask a string manufacturer
what criteria they use in designing strings and string sets you are
unlikely to receive a useful answer (I know because I asked them all!).
Answers you do get range from “we don’t know, we just make
them to the formula set years ago” to “we could tell you,
but we would have to kill you” or “we make them pretty much
like the other string companies because it’s what the customers
String set tensions
Until about 150 years ago
string design was mostly trial and error. Then the general level of
engineering knowledge and technology developed to the point were it
could be applied to the existing practical experience and clear design
principles were established. For example the following formula shows
the relationship between tuning tension, physical properties, and the
fundamental vibrating frequency of a string.
T = (UW x (2 x L x F)2) /
Where T is tension in lbs
(strictly speaking, Pounds are a measure of mass and not tension. String
tensions given in pounds can be converted to Newton’s by multiplying
by 4.45), UW is unit weight of the string in lbs per linear inch, L
is vibrating length in inches and F is the fundamental vibrating frequency
To make use of this formula
you need to know one key property of a string; it’s Unit Weight.
This can be arrived at using two different methods, either by accurately
weighing a known length of string or by measuring the diameters of the
core and wrap wire (if the string has one) and calculating unit weight
using the known densities of the materials.
You might expect the gauges
of a string set to be chosen so that, when tuned to pitch, all six strings
would be at the same tension, providing the guitarist with a consistent
feel across the set, or at least for there to be an obvious relationship
in the tension values across a set, for example, a smooth increase in
tension from treble to bass. In practice all string sets exhibit large
differences in tension across the set.
Apart from Thomastik Infeld,
who publish tensions for their string sets on their website, only major
manufacturer D’Addario, publishes a complete string tension table
and prints individual string tensions on their set packets. Without
published tensions for every available string brand it takes a bit of
research to find out just how widely string tensions vary and that,
although there is a consistent pattern to the tensions within sets,
across all manufacturers, there is no obvious logic behind it. It is
quite common for there to be at least a 30% variation in tension across
a string set.
If you compare the set gauges
of commercial acoustic guitar string sets from all the string manufacturers
you will find they are made up of almost the same gauges. For example
the maximum gauge variation for light (0.012 e string) acoustic set,
out of all strings in a set is only 0.004 between a 0.022 and 0.026
g string and the average differences in gauge for the same string in
sets from different brands are even smaller at only 0.001 of an inch
difference in diameter. These tiny differences do have more of an effect
than you might at first think because tension is related to the square
of string diameter. Doubling the diameter of a string quadruples the
tension. Greater differences occur in the custom and signature sets
and in the sets designed for playing certain styles such as bluegrass.
In this graph of string set gauges the curved brown line shows the gauges
required for an equal tension set (starting with an 0.010 e’)
compared to the actual gauges found in the D’Addario commercial
In this graph the corresponding
tensions are shown for the same sets plotted in the gauges graph. All
the set tensions exhibit the same characteristic ‘sickle’
shaped plot. Notice the ‘crossovers’ for the custom light
and bluegrass sets with the slightly heavier lower strings. The flat
‘perfect equal tension’ line is included for comparison.
What is significant is that
string set tensions for standard acoustic steel strung guitar in EADGBE
tuning, follow the same patterns, across the industry. In general for
any medium set starting with a 0.013, the top two plain strings are
at roughly the same tension, the third string (usually a wound string)
forth and fifth strings increase in tension by about 30% and finally
the bottom string tension is only 6 to 10% higher than the first two
plain strings. As the overall gauge of the sets varies from extra light
to light to medium (the term ‘heavy’ for an acoustic string
set isn’t normally used now, perhaps because marketing departments
feel it might put customers off) this pattern of relative tensions across
the set remains, although of course all the tensions across a set increase
as you go from extra light to medium sets (see the tension graph above
for a clearer picture of string set tensions).
This graph shows the tensions for strings set for different guitar types.
Tensions shown are for D’Addario phosphor bronze EXP sets, plus
a Newtone resonator set and two La Bella Baritone sets for comparison.
D’Addario’s resonator set is intended for the d’bgdBG
lap Dobro tuning and so exhibits very different tensions to the Newtone
It is perfectly possible
for the string manufacturers to assemble equal tension sets for standard
tuning, or for any of the common open and alternate tunings. It is even
possible to buy off-the-shelf, standard gauge, single strings to make
up a set that comes within a few pounds of equal tension, without resorting
to custom gauges. So why do the string manufacturers compose their string
sets with such uneven tensions? Since string manufactures aren’t
prepared to reveal their reasoning we can only make an informed guess.
The most obvious transition
is between the top two plain strings (all my examples given here are
for 2 plain 4 wound sets) and the other four wound strings and this
is clearly evident in all the graphs. The core dimensions for the 3rd
and 4th strings are commonly smaller than the plain 2nd. Bigger gauge
strings are louder, so it seems that the bigger gauges (core plus wrap)
for the g, d, A and E strings compensate for the effect of the small
cores and are necessary to obtain a volume balance across all six strings.
This seems considered to be more important than an even string tension
across the set. Since volume balance will depend to some extent on each
particular guitar, presumably string set tensions are chosen as a best
guess compromise to suit the ‘average’ guitar.
A plot of the gauges and core diameters for both an ‘equal tension’
set and the D’Addario EXP16 set, show that the core diameters
for the 3rd and 4th strings are smaller than the plain 2nd.
For the more exotic instruments,
such as National resonators, Dobros and Baritone guitars, where there
is less market pressure to conform, individual manufacturer’s
ideas on the correct string set become much more evident and there is
greater variation in string set make up between the brands.
Strings & the musician
All this detailed information
on string construction and design is all very well but what use is it
to the musician?
Well there is a considerable
choice of string types and gauges on the market, with new variations
being added all the time, so understanding strings at least helps you
to see beyond the marketing hype to select the most appropriate standard
string set for your style and instrument. If you are buying strings
in a guitar shop it isn’t always evident what variations are available
and you might not realise that specialist sets, like the bluegrass set,
even exist. Taking it further; knowledge of string set design helps
the guitarist looking for their own sound. Individual string gauges
can be selected to make a custom set with a slightly different tonal
balance, or to better suit playing in an open or altered tuning. For
example; conventional wisdom says that you would never use electric
strings on an acoustic guitar, however fingerstyle master John Renbourn
says on his website that for many years he used sets of nickel electric
strings when playing his acoustic using a magnetic pickup. Nickel strings
could also perhaps be used to brighten up an otherwise very dull sounding
acoustic guitar. Conversely it makes sense to use phosphor bronze or
even copper wound strings on a naturally very bright instrument. Or
perhaps a mixed phosphor bronze, bronze set could be used to obtain
an unusual tonal balance. DR Strings make sets of what they call Zebra
strings with alternate strands of phosphor bronze and nickel plated
steel wrap wire, for a bright acoustic tone and great performance with
a magnetic pickup. The so called gypsy or manouche style silver plated
copper wound strings have a very interesting tone and are worth checking
out for playing other styles than gypsy jazz.
The mystery of string set
I have been very puzzled
by the tension characteristics of commercial string sets revealed during
my research for writing this article and, using the tension information
from the tension chart published by D’Addario, I decided to try
a limited experiment. I was able to select six individual strings for
EADGBE tuning, from the standard range of D’Addario gauges, with
a much closer to equal tension than their standard packaged sets. I
tried this set on an Alvarez Yairi DY66 dreadnought with a cedar top
(so this guitars nature is to be warm and loud). This ‘custom’
set is very comfortable to play, there is no obvious volume imbalance
across the six strings and the overall sound is very good indeed, not
lacking in volume and lively without being over-bright. I used the following
gauges - 0.012, 0.016 plain and 0.021, 0.029, 0.039 & 0.049 phosphor
bronze wound, for this set, giving the following tensions of 23.3, 23.3,
23.1, 25.2, 25.4 & 22.5. The maximum tension difference is about
14% across the set, compared to nearly 39% for a standard set of D’Addario,
or in fact almost any other manufacturers, set of light gauge strings.
Browse to www.daddariostrings.com
and select – Support – FAQ – Product assistance, select
the seventh question down about a tension guide and you can download
a PDF file of the D’Addario tension guide.
Coming up in part 2 in the
In part two of this feature
on strings I’ll be explaining exactly why strings break, why they
wear out and lose their tone and how to install new strings to minimise
tuning problems. I’ll look at long-life strings, cryogenic hardening
and nylon strings in more detail
There will also be a table listing all string manufacturers, along with
the types of strings they make and a graph comparing the cost of string
By – Terry Relph-Knight
CREDITS - My thanks for their help in preparing this article to –
Jason How at Rotosound, Frank Ford for the three string pictures, Brian
Vance, Sr. Brand Manager, Fretted products at J.D’Addario, Jim
Cavanaugh for the Super-Sensitive Musical String Co., Craig Theorin
Product Manager Elixir® Strings W. L. Gore & Associates, Inc.,
Malcolm Newton of Newtone Strings, Brian Ball at Ernie Ball inc., Greg
Orred at GHS, Paul Mason at Sfarzo Strings, Pete at Rohrbacher Technologies
and anybody else I pestered with daft questions about strings and have
inadvertently omitted from this list.