EffectsofWoodAttributesonAcousticGuitarSoundQualityJanEmanueleBartolome

ABSTRACT

Theguitarisaclassicinstrumentthat’sbeenaroundforhundredsofyears.Thesoundqualityofaguitarcanbeattributedtothewoodusedtoconstructit.However,soundqualityismorequalitativethanquantitative.Amoreexpensiveguitarisnotnecessarilyabetterguitar.

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Introduction

Theguitar,whichis“astringedmusicalinstrumentwithalong,frettedneck,aflat

somewhatviolinlikebody,andtypicallysixstrings,whicharepluckedwiththefingersor

withaplectrum”[1]isoneofthemostwellknowninstrumentsintheworld.Researchers

believethattheguitaroriginatedfromtheguitarralatina,aninstrumentinventedinSpain

intheearly16thcentury[2].Thoseguitarswerecomposedoffourstrings,tunedtothenotes

C-F-A-D[2].Nowadays,guitarsaremadewithsixstrings,andaretunedtothenotesE-A-D-

G-B-E.

Theprimarymaterialusedinmakingguitarbodiesiswood,andthetwomainpartsofthe

guitarthatusewoodaretheneckandthebody.Differentspeciesofwoodcanbeusedfor

eachpart,orthesamecanbeused.Thespeciesofthewoodgreatlychangesthesoundand

toneoftheinstrument.SomeofthecommonwoodsusedincludeAlder,Ash,Basswood,

Korina,Mahogany,Maple,Poplar,RosewoodandWalnut.Woodsofthesamespeciescut

fromdifferenttrees(orgrownindifferentregions)willsoundslightlydifferent,andhave

differentweights,differentdensities,andsoon[3].TaylorGuitarsisoneofthelargestand

mostpopularproducersofguitars.Thethreemostpopularmodelsarethe114ce,214ce,

and814ce.Table1showsasummaryoftheprice,andwoodtypesofthesethreeguitars.

Guitar Price(USD) WoodTypeUsed

114ce 1,058 Back/Side–LayeredSapele

Top–SitkaSpruce

Neck-Sapele

Fretboard-Ebony

214ce 1,328 Back/Side–LayeredRosewood

Top–SitkaSpruce

Neck-Sapele

Fretboard-Ebony

814ce 4,498 Back/Side–IndianRosewood

Top–SitkaSpruce

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Neck–TropicalMahogany

Fretboard-EbonyTable1:ComparisonofpriceandwoodtypeusedforthreedifferentmodelsofTaylorguitars

FromTable1,itcanbeobservedthatthetopthreemostpopularguitarsmadebyTaylorall

haveaSitkasprucetopandsapeleorrosewoodbacksandebonyormahoganyfretboards.

TaylorGuitarsaysthat,“Whiletherichtonesofsolidwoodremainunmatched,alayered

woodconstructioncanyieldgreatsoundinabeautiful,durableandaffordableinstrument.

Suchisthecasewithlayeredsapele,inwhichweuseinteriorandexteriorveneersofsapele

withacorelayerofpoplarbetweenthem”[4].

Therehavebeenmanyrecentdevelopmentsinguitartechnologyovertheyears.Onesuch

exampleislayeringwoodsfortheneckinsteadofusingonesolidpiece.Thisallowsfor

moreflexibilitywhereguitarswithbettersoundsusinglowerqualitywoodcouldbe

achieved.Otherinnovationsincludetheuseofmaterialsthatarenotnecessarilywood,but

arecarbonfiberorfiberglass,orgraphite.Forexample,Adamasgraphite-topacousticis

betterprotectedagainsttemperatureandhumiditychangescomparedtothetraditional

sprucetop[5].Thermowoodisanotherinnovationbeingusedformakingguitars.

Essentially,thewoodisbakedinanoventocreateavintage,crispsound[6].Lastly,Acoustic

ResonanceEnhancement(ARE)isanewwayoftreatingwood.Itissimilartothermowood

inthat“newwoodmaturedwiththistechnologyproducesatonalrichnesslikethatofwell-

usedvintageinstruments”[7].

GuitarAnatomy

Inaguitar,thesoundcomesfrompluckingorstrummingthestrings.Thestringsare

connectedtotheneckandthebodyofaguitarthroughthesaddleandtheheadstock.

Figure1showsadiagramofaguitaranditsdifferentparts.

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Figure1:Diagramofaguitar[8]

Thebodyiswhatresonatesthesoundofthestringsbeingpluckedorstrummed.The

generallyaccepteddesignisforthesoundholetobeinthecenterofthebody,asthis

makesitmoresymmetricandappealing.However,thisactuallystructurallyweakensthe

soundboard,ortopofthebody[9].Oneimportantpartofthebodyistheheeljoint.“The

heeljointreferstothecurvedblockofwoodthatisusuallyfoundonanacousticguitarat

thepointwheretheneckjoinsthebody”[10].“Steelstrungguitarswitha‘traditional’neck

jointhaveawoodblockinsidetheguitarandtheneckisjoinedtothisblockwithadovetail

join.Thedovetailiscarvedintotheinsidefaceoftheheelandsecuredtoamatchingcavity

inthebodyblockwithglue”[10].

Theneckiswhatholdsthefretboardofaguitar.Itisconnectedtotheheeljointofthebody

andontheotherendisconnectedtotheheadstock.Thisisoneofthemostimportantparts

oftheguitarbecausethisiswherethefeelofaguitaranditsplayabilityaremost

observable.Anotherpartoftheneckisthetrussrod.Itisametalrodthatisplacedinside,

alongthelengthoftheneck.Itisusedtostiffentheneckoftheguitaraswellasto

“counteracttheforceofthestrings,whichtendstobendtheneckforward”[10].Thetruss

rodcanalsobeadjustedtobendtheneckatahigherorloweranglefromtheheeljoint.

Thiscanchangethefeeloftheguitarbyeitherincreasingordecreasingthespacebetween

Heeljoint

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thestringsandthefretboard.Ahigherspacemakestheguitarhardertoplay,howeverif

thespaceistoosmall,thereisariskofthestringshittingthefretboardandproducingan

unpleasantbuzzingsound.

Differentwoodsareusedforthebodyoftheguitar.“Thetopofsoundboardwoodsare

usuallychosenfortheirstrengthandacousticpropertieswhilethesides,orrims,andback

woodsarechosenmorefortheirappearanceandabilitytobesteambentintocurvesfor

thesides“[9].Fortheneck,themostcommonlyusedwoodismahoganyasitcarveseasily

andhasgoodlongitudinalstrength.Taylorusesanotherwoodcalledsapele,andaccording

tothem,“it’ssometimesmistakenlyreferredtoasAfricanmahoganybecauseitclosely

resemblestheWestAfricanwoodkhaya,whichiscommerciallyknownasAfrican

mahogany”[11].

Tonewoods

Tonewoodiswoodthatcreatesacertainsoundortonewhenstruck.“Ifaguitar’sbody

shapeproducesthesonicequivalentofameal,thinkoftonewoodsastheseasoning”[12].

Therearemanytypesofwoodavailableintheworld,however,tonewoodsarespecial

becausetheycreateasoundwhenstruckandresonatethatsoundwell.“Becauseofthe

dynamicsoftheguitar,tonewoodsforfacesneedtobedifferentthantonewoodsforbacks,

iftheinstrumentistohavethebestandmostevensound”[13].“Lighter woods like mahogany

are said to have a dry and woody sound. The denser Rosewoods have a rich and bell-like sound,

while the denser-still Ebonies and Blackwoods are said to impart a deep, piano-like sound to the

guitar” [14].

Forthetop,spruceisthemostpopularwoodtouse(Table1).“Asaguitarsoundboard,or

top,Sitkaspruceisthetonewoodstandardofthemodernera.It’susedon85-90percentof

theguitarsthatTaylormakes.Itscombinationofstrengthandelasticitytranslatesintoa

broaddynamicrange,yieldingcrisparticulationandallowingforeverythingfrom

aggressivestrummingandflatpickingtofingerpicking.SitkaspruceisBobTaylor’s

personalfavoriteforanall-aroundgreatguitar”[15].Therearetwotypesofsprucewoods

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used:(1)EuropeanSpruce,whenbentorstressed,willcrackandbreakbecauseitisbrittle.

However,itcreatesverygoodovertonesandamorefullsound.(2)AmericanSpruceis

strongandwillnotbreakwhenbentorstressed,howeveritcreateslessovertonesanda

warmerfeel.Thisisgoodformusicsuchasfolk.

Usuallythetopofthebodyisadifferentwoodcomparedtothebackofthebody.“Thebest

guitarbacksaremadeofhighqualityhardwoodssuchasrosewood,ebony,maple,walnut,

koa,mahogany,oranumberofothersuitablebodywoods”[13].InthecaseofTaylor,their

threemostpopularmodelshaveeitherasapele,orarosewoodback.Traditionally,

Brazilianrosewoodhasbeenusedbecauseofitshighqualityresonance.“Whenstruck,a

properlycutsampleringslikeaplateofglass”[13].Thisisagreatqualityforaguitar

becauseithelpswiththeresonanceandwillallowtheguitartosustainthesoundfora

longertime.ThealternativetoBrazilianrosewoodisIndianrosewood.Thishasthesame

propertiesastheBrazilianrosewood,butisnotasgoodatresonatingandsustaining

sound.ThereasonforanalternativeisthedecliningamountofBrazilianrosewood.

Toobtainwood,treesmustbecutdownfromtheforest.Inthecaseofrosewood,Brazilian

rosewoodisoneofthebestchoices.Becauseofthis,Brazilianrosewoodhasbecomemore

scarceandisonCITESAppendixI,whichmeansthatevenfinishedproductsofthiswood

arenotallowedtocrossinternationalborders[16].ThisisthemainreasonthatIndian

rosewoodhasbeenusedasasubstitute.ThesoundisverysimilarandIndianrosewoodis

moreavailable.AnotherexampleofwoodsusedinguitarthatisbecomingscarcerisEbony.

Ebonyisusedmostlyintheneckandonfretboards.“Theissueisn’trocketscience:ebony

trees(intheDiospyrosgenus)aregenerallysmallandslowgrowing.Demandforebony

woodisveryhigh:it’sahighqualityhardwoodthat’sveryhard,verystrong,andmostof

all,veryblack”[17].Mostoftheworld’sebonycomesfromthird-worldcountriesandsoit

hasbeenexploitedtonearextinction.TaylorusesMacassarebonyandAfricanebonyin

theirguitars.Toobtainthisebony,theyhavepurchased“Crelicam,anebonymilllocated

outsideofYaoundé,Cameroon”[18].Thisistoensure“thatebonyislegally,sustainably,and

ethicallyharvested”[18].

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Scientificanalysisofsound

Thesoundofaguitarisproducedinthestrings.Thebodyiswhatresonatesthesoundand

thetypeofwoodiswhat‘colors’thesound.Thebridge,whichconnectsthestringstothe

body(morespecificallythetop),“transfersthevibrationalenergyofthestringstothetop

plate”[19].Thetopthenvibratesandtransfersthevibrationstotheairinsidethebodyof

theguitarandoutthesoundholeamplifyingthesound.“Thetopplateismadesothatitcan

vibrateupanddownrelativelyeasily.Ontheinsideoftheplateisaseriesofbraces.These

strengthentheplate”[20].Itisalsonecessarytonotethatthebodydoesnot“amplify”the

soundinthetraditionalsenseoftheword.Forcomparison,inelectricguitars,thevibration

fromthestringdisruptsthemagneticfieldaroundthepickup,whichisaseriesofmagnets,

andthepickupsendsthisdisruptiontotheamplifiertocreatealoudersoundthatcanbe

heardthroughspeakers[21].Inacousticguitars,“allofthesoundenergythatisproducedby

thebodyoriginallycomesfromenergyputintothestringbytheguitaristsfinger”[20].The

bodythendoestheequivalentofwhatanamplifierdoesbystrengtheningthesoundinside

thebody.

Oneofthemainfactorsthataffecttheacousticpropertiesofwoodisitsdensity.“Themost

importantacousticalpropertiesforselectingmaterialsforsoundapplications,suchas

musicalinstrumentsandbuildinginteriors,arethespeedofsoundwithinthematerial,the

characteristicimpedance,[and]thesoundradiationcoefficient”[22].Thegrainofthewood

anditsdirectionaffectsthespeedofsound.Inaguitar,characteristicimpedanceis

importantbetweenthebridgeandthebody.Thetwomediumshavedifferentimpedances

tosoundandacarefulratiomustbemadebychangingthicknessofeachmedium.

“Sufficientvibratoryenergymustbetransmittedformthestringtothesoundboardto

makethestringsvibrateaudibly,whiletheenergyshouldnotbetransmittedtooreadilyor

toorapidly,causingthevibrationsofthestringtodiedownquicklyandtheirsoundto

resemblethatofathud”[22].Thesoundradiationcoefficientreferstothedampeningofa

vibrationinabodyduetosoundradiation.Thisisimportantinguitarsforhowlongthey

cansustainasound.

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Withthesepropertiesinmind,adifferencecanbemeasuredbetweennewguitarsandaged

guitars.Luthiersandexperiencedguitarplayerswillsaythatvintageguitarshaveabetter

toneandsoundqualitybecauseoftheagedwood.“Onebitofscience[LuthierAlan

Carruth]hasbroughttotheattentionofthelutheriecommunityisthatwoodconsists

mainlyofcellulose,lignin,andhemicellulose,andthatallwoodgraduallyloses

hemicellulose—asolublepolysaccharide—toevaporationoveralongperiodoftime”[23].

Thismeansthataswoodages,itlosesweightandtensilestrengthovertime,butthe

stiffnessisnotlostasquickly.“Aslongasthetensilestrengthremainssufficientto

withstandstringtension,thereisanetgaininoneofthemostimportantfeaturesof

tonewood:thestiffness-to-weightratio,whichisknownasYoung’smodulus”[23].

PrimaryResearch

Oneofthebiggestopiniondifferencesinguitarscomesinhowaguitarsounds.Thisis

becauseeachpersonhearsthingsdifferentlythanthepersonnexttothemlisteningtothe

samething.Theywillheartheexactsamesoundwaves,howevertheirbrainwillinterpretit

differentlyandthesoundwillgivethemadifferentfeel.Thesoundofaguitar,whileitcan

besomewhatquantifiedintermsofdecibels,ismorequalitative.Forthisveryreason,I

wenttoamusicstore,LongandMcquadelocatedinVancouver,BC,andtestedoutthe

threeTaylorguitarsmentionedearlier.Iplayedeachoneforabout20minutesandplayed

theexactsamethingoneachguitar.Herearetheresults.

Taylor114E(899CAD)

TheonlydifferencethatthisguitarhaswiththeTaylor114CEisthatitlacksthecutawayin

thebodythatallowsplayerstoreachhigherfretswithmoreease.“The114edefiesthe

logicofmoststarterguitarsbyprovidingareallygreat-soundinginstrumentthatextremely

well-built.Laminatedsapelebackandsidesandasolidsprucetopmakeforcrispandwell-

definedsoundinthisversatilemid-pricedguitar”[24].Inmyopinion,thisguitarfeltheavier

thantheothertwomodels.Purelyonaestheticsalone,Iwasnotabigfan.Thedotsonthe

frets,aswellasthedesignonthesoundhole,lookedliketheywerepaintedonorwere

stickers.Thesoundwasnottoopowerful,butgoodforpluckingsoftly.Iwashopingtohear

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thebrightwarmsoundthatisassociatedwithTaylorguitars,howeverIfoundthesoundto

beslightlydampenedandmore‘twangy’.Icouldnotheartheovertonesasmuchandthe

notesweresustainedforonlyashorttimebeforesoundingdead.Thisguitarisgoodfor

beginnersbecauseitwastheeasiesttoplay.

Taylor214CE(1,399CAD)

It’s“aglossy,solidSitkasprucetopmeetsgorgeousIndianrosewoodlaminatebackand

sides,deliveringanexperienceofsight,soundandtouchthat’sunmistakablyTaylor”[24].In

myopinion,thiswasexactlywhatTaylorguitarsshouldsoundlike.Itwasbrightandwarm,

perfectforstrummingandlightplucking.Thisguitarwouldplaynicelywithfolkmusicor

slowjazz.TheplayabilitywasreallyeasyandIfoundthatIlosttrackoftimewhileplaying

it.ThesoundwasveryfullandfilledthelittleroomIwasinwithnoeffort.Therewasa

slighthintofovertones,butnothingtooobvious.Ireallylikedtheaestheticsofthisguitar’s

neckduetothewoodgrainofthelayeredrosewood.Overall,thiswasmyfavoriteofthe

threeanditwasthemostreasonablypriced.

Taylor814CE(4,899CAD)

Thisguitar’s“balance,warmthandarticulationaregreatforfingerstyle,ithasenough

punchasastrummertofrontaband,andthetop-endpowerwillfuelleadrunswithout

gettingshrill.It’sagreatchoiceforagiggingplayerlookingforoneguitarthatcancoverit

all”[25].Aesthetically,ithadpearlinlaysonthemarbledfretboard.Thecolorsoftheguitar

wereveryeyecatchingandlookedvintage.Thesoundwasfullandfilledtheentireroom

effortlessly,meaningyoudidn’tneedtostrumorpluckthestringsashardasyouwouldon

theothertwo.Theovertoneswereveryobviousandthesoundwassustainedforalonger

periodoftime.Thedownsidetothiswasthattheneckwasnotassmoothbecauseofa

finishingvarnishonitandtheaction(spacebetweenthefretandthestrings)wasmuch

higher.ThismadetheguitarlessplayableanditdidnotfeelasnicetoplayastheTaylor

214CE.

Aftertryingthesethreeguitars,myfavoriteguitarintermsofsoundandplayabilitywas

theTaylor214CE,althoughaesthetically,theTaylor814CEwasthebest.Iamnotanexpert

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whenitcomestoguitars,howeverIhavebeenplayingformorethantenyearsandsoI

thinkthisqualifiestheobservationsImadeabouteachguitar.

OneinterestingthingthatInoticedwasthatalltheguitarssoundedthesamewhenplugged

in.Thisisprobablyduetotheguitarpickupsystembeingthesameinallthreeguitars.

Whenpluggedintoanamp,alltheguitarssoundedexactlythesame,sothequalitative

observationsImadeaboutthesoundwerenullified.

TechnologicalAdvances

Newandinnovativetechnologyisbeingreleasedeverydayandthisholdstrueforguitars.

Thesetechnologiescanrangefromimprovingthesoundsystemthatallowsaguitartoplug

intospeakers,newmaterialsforstrings,andmostimportantly,changingthewaythewood

usedforguitarsistreated.

Oneinnovativewayofchangingthewoodinaguitarhasbeenmentionedearlier.Layered

wood,ormorecommonlyknownaslaminatedwood,isusedinmanyguitars(forexample

theTaylor114CEandTaylor214CE).Thelaminatedwoodiscomposedofalayerofan

expensivepieceofwoodoverlayersofcheaperpiecesofwood.Thismakestheguitarless

expensive.AccordingtoTaylor,“Oneofthebenefitsoflayeredwoodforguitarsisextra

resilienceinthefaceoffluctuatinghumidityconditions”[4].Onedrawbackoflayeredwood

isthatithasaflattersoundanddoesnotproduceasmuchvolumeascomparedtoasolid

piece.Thisisbecauseitdoesnotvibrateaswellduetoitslayers.

YamahaisalsodevelopingatechnologycalledAREorAcousticResonanceEnhancement

Thisnewtechnologyisawayoftreatingwoodtomakeithaveamaturesoundandthe

tonalcharacteristicsofvintagewood.Oneofthebiggestthingstheaffectswoodin

instrumentsisheatandhumidity.WhatYamahafoundwasthat,“Youngwoodgivesan

edgeandhardnesstothesound,but,astheyearspassby,itbecomesmoreandmore

difficultforchangestooccuranditproducesagooddeep,roundedsound”[26].Theway

thatYamahadiscoveredtocreatethissoundinyoungwoodwasbycontrollingthe

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humidity,temperature,andatmosphericpressure.Thistreatmentaffectsthegrainofthe

wood.“Thehardeninginthedirectionofthegrainandsofteningacrossthegrainofthe

woodachievedbytheAREtreatmentimprovestheclearnessofthesound,makingit

unmuffled,andproducesexcellentresonancebyenhancinglowrangesustainand

increasingtheattackinthemedium-tohigh-rangefrequencybands”[26].

Anotherinnovationthatisworthlookingatisthermowood,whichisaprocessthatwas

developedinFinland.Thermowoodisessentiallywoodthathasbeenheat-treatedto

increaseitsstrengthproperties.Thewoodistreatedatlowoxygenlevelstopreventitfrom

burning.“Temperaturesfortheactualheattreatmentperiodrangefrom150°Cto240°C,

thetimeoftheperiodis0.5to4h”[26].Acompanynamed‘Sago’isusingthisthermowood

intheirguitarsbecauseitgivesitamorevintagesoundandmakesitmoredurable.

AccordingtoSago,“balancebetweenstringsandfretswillincrease.Thermowood

processingkeepsthebodysizestableinhumidJapan,preventingdeformationofyour

instrumentathomeorinacar,orevenagainstspotlightsandheatoftheaudienceata

performance”[6].

Summary

Theguitarisatimelessinstrumentthatisonlygettingmorepopularastheyearsgoby.

Thispopularitycanbeattributedtoitsconvenientsize,it’splayability,andthegreat

soundsthatitproduces.Therearemanytypesofguitarsandtheyareallmadewiththe

samegeneralblueprintinmind.Thedifferencesarebasedonthewoodchosenforspecific

partsandtheshapeinwhicheachoneisbuilt.Othernotableinstrumentsthathavea

similarbuildandstyleofplayinclude:ukuleles,mandolins,basses,andbanjos.

Thesciencebehindthesoundofaguitarcanbesummarizedintothewood’sdensityand

thestiffnesstoweightratio(alsoknownasYoung’smodulus),aswellashowthesound

actsandmovesinsidethebodyoftheguitar.Thefactorsofthespeedofsoundintheguitar,

itscharacteristicimpedance,andsoundradiationcoefficient,allplayalargepartinthe

acousticproperties.Thesearespecificthingsthatcanbemeasuredwithscientific

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instrumentsinsidealab.Manyworksofliteraturegomoreindepthonthespecificsof

soundinaninstrument;however,Ihavefoundthatthesoundofaguitarisdependenton

theearandsoundperceptionofthepersonlistening.Whendescribinghowaguitarsounds,

thetermsusedaremorequalitativethanquantitative.Theaverageguitarplayerwouldnot

beabletotellyoutheacousticpropertiesofthewoodintheirguitar,buttheycantellyou

thatit“soundswarm”or“itcreatesabrighttoneandproducesloudovertones.”Noneof

thesedescriptivequalitiesarequantitativeandisallbasedontheguitarist’sperceptionof

thesound.Withintheguitarcommunity,therearedisagreementsonwhetheravintage

guitarsoundsbetterthananewerguitarbecauseofitsagedwood.Therehasbeenresearch

donetosupportthis,suchastheincreaseinstiffnessaswoodages,buttheadvancements

inwoodtreatingtechnologyismakingthoseargumentsnull.Treatmentshaveadvancedto

thepointneworyoungwoodis“aged”andthusthesounditproducesisvintage.These

advancementsarealsoaffectingnewguitarsinthatcheaperguitarsaresoundingbetter

evenwithlowerqualitywood.Amoreexpensiveguitardoesnotnecessarilymeanthatitis

goingtobebettersoundingormoreplayablethananexpensiveone,aspermyobservation

betweentheTaylor814CEandTaylor214CE.

Theguitarisaclassicinstrumentthathasundergonemanychangesovertheyears.There

arealwaysmoreimprovementstobemadetobringittothenextlevel.Itisexcitingtosee

wheretechnologyispushingtheboundariesofguitarmakingandthesoundsitcan

produce.Fromthermowoodtoacousticresonanceenhancement,thefutureofguitarslooks

bright.Asaguitarplayer,Ibelievethatthecurrentstateoftheguitarisperfect,butIam

eagertoseethedevelopmentsbeingmadeandwhereitwilltakethisinstrumentthathas

beenaroundforhundredsofyears.

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AppendixA–CommonTonewoods

CommonName LatinName AverageDriedWeight(kg/m3)

Sapele Entandrophragmacylindricum

670

SitkaSpruce Piceasitchensis 425

Macassarebony Diospyroscelebica 1,120

BrazilianRosewood Dalbergianigra 835

IndianRosewood Dalbergialatifolia 830

AfricanMahogany Khayaspp. 640

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References[1]"TheDefinitionofGuitar."Dictionary.com.Web.06Apr.2016.[2]"HistoryoftheGuitar."HistoryoftheGuitar.Web.06Apr.2016.[3]Hunter,Dave."AllAboutTonewoods."AllAboutTonewoods.Web.06Apr.2016.[4]"LayeredSapele."TaylorGuitars.Web.06Apr.2016.[5]Potts,Paul."GeekVersusGuitar."RecentDevelopmentsinGuitarTechnology.Web.06Apr.2016.[6]"Thermowood:AboutSago'sNeckMaterial."Sago.Web.06Apr.2016.[7]"A.R.E.Technology."Yamaha.Web.06Apr.2016.[8]AcousticGuitarParts.Squarespace.Web.[9]Relph-Knight,Terry."TheAcousticGuitarBody–Part1."AcousticMasters.Web.06Apr.2016.[10]Relph-Knight,Terry."TheGuitarNeck&Fretboard."AcousticMasters.Web.06Apr.2016.[11]"Sapele."TaylorGuitars.Web.06Apr.2016.[12]"Woods."TaylorGuitars.Web.06Apr.2016.[13]Somogyi,Ervin."TonewoodsinGuitars."Esomogyi.Web.06Apr.2016.[14]Brill,Andrew,andDrewBeeson."TheAcousticalPropertiesofWood."(2007).Web.[15]"SitkaSpruce."TaylorGuitars.Web.06Apr.2016.[16]"BrazilianRosewood."TheWoodDatabase.Web.06Apr.2016.[17]Meier,Eric."Ebony:DarkOutlookForDarkWoods?"TheWoodDatabase.Web.06Apr.2016.[18]"SustainableEbony."TaylorGuitars.Web.06Apr.2016.[19]"AcousticGuitar."Hyperphysics.Web.<http://hyperphysics.phy-astr.gsu.edu/hbase/music/guita.html>.[20]Wolfe,Joe."HowDoesaGuitarWork?"TheUniversityofNewSouthWales.Web.

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[21]"HowElectricGuitarsMakeSound."SoundCalledMusic.Web.06Apr.2016.[22]Wegst,UlrikeG.K."WoodforSound."AmericanJournalofBotany93.10(2006).Web.[23]Turner,Rick."AcousticSoundboard:TheSonicEffectofTimeandVibration."PremierGuitar.Web.06Apr.2016.[24]"AcousticGuitars."Long&Mcquade.Web.06Apr.2016.[25]"814ce."TaylorGuitars.Web.06Apr.2016.[26]Homan,WaldemarJ.,andAndreJ.M.Jorissen."WoodModificationDevelopments."(2003).Web.