Today, I will be talking about guitars, a subject close to my heart as I have quite a collection of them. I will describe the evolution of the modern guitar and mention some of the more interesting items in my collection.

I should briefly describe the parts of a guitar as I will be referring to them throughout this article. A guitar has a body and a neck and a head which is sometimes called the headstock. The strings are attached to the body and vibrate between a point on the body called the bridge to a point at the end of the neck called the nut. There are raised strips on the neck called frets. Notes are selected on each string by pushing the string down to the neck which effectively shortens the string to the length between the fret and the bridge. This changes the wavelength of the vibration in the string and so increases the frequency. Hollow bodied guitars normally have one or more soundholes to project the sound forward.

Guitars have existed in various forms since the 15th century. Of course, these were acoustic instruments which relied on their body shape for sound projection. The elements that we would expect are all there in the early design but with some interesting differences. The body of the guitar was longer and thinner than a modern guitar and the strings were gut rather than the more familiar steel or bronze of modern guitars. The sound would have been like a quiet classical guitar that uses nylon strings. The strings were tied to the bridge and to the tuning pegs at the head of the guitar. One obvious difference was the number of strings. Early guitars had 4 or 5 courses of string – a course could be a single, pair or triple string. Modern guitars have 6 strings except for bass guitars and some of the electric guitars used for heavy detuned rock. 12 string guitars are actually a revival of an older idea since they are 6 courses of 2 strings, each tuned to the same note but in the case of some strings, tuned an octave apart. Original guitars had bowl (curved) backs – a concept revived by the Ovation guitar company. The frets were generally strips of gut tied around the necks of the guitar. The fret allows accurate pitching of notes as I will describe later.

From the original design of the guitar, many variants have arisen. Here are some of the main types of which there is a bewildering number:

1. The Classical guitar

This is the clearest descendant of the original guitars. These are typically figure of eight shaped guitars with the upper part of the body narrower than the lower – they have a pronounced waist as most acoustic guitars do. They are nylon strung and have a fixed bridge with no method for altering the intonation which I will explain when I come to electric guitars. The front of the guitar body forms a soundboard as is usual with acoustic guitars with the back of the guitar having a lesser influence.

Cheaper contemporary models will use a composite (plywood) soundboard. More expensive models will have a high quality spruce top. The soundboard will typically have a pattern of bracing struts hidden out of view. Various woods are used for the back and side. Frets are almost invariably metal on modern guitars. Classical guitars do not normally have a pickguard which is a plate for protecting the top of the guitar from pick scratches since classical guitars are usually played fingerstyle. Fingerstyle is where individual notes or sometimes pairs of notes are played rather than entire chords – and they are played with the fingers rather than a pick as the name suggests. Classical guitars produce little volume and were generally restricted to parlour use until amplification became available.

2. The Spanish guitar.

The Spanish guitar is similar to the classical except that it has one or perhaps two plates on the soundboard that can be used for tapping to produce percussive effects. There are also two variants used in Mariachi called the vihuela and the guitarro which are respectively smaller (and higher pitched) and larger (and lower pitched) than a standard guitar. Unlike the classical, Spanish guitars are sometimes strummed to play chords as well as being played in the classical fingerstyle.

3. Folk guitars

These are a very common type of guitar. Outwardly similar to the classical guitar, these have a large body (especially the type known as dreadnought) and have metal rather than nylon strings. To take the additional stress, the necks of folk guitars have one or rarely two truss rods – metal rods which contain an adjustable screw allowing the tension of the neck to be adjusted against the pull of the strings. They can be played like a Spanish guitar although they are not normally struck for rhythm effects. They are often played with a flatpick or plectrum to strike the strings harder. Folk guitars (often just called acoustic guitars) are much louder than classical guitars and can fill quite an area if played with vigour as many buskers have demonstrated. Some acoustic guitars have a cutaway which is a change in the lower shoulder of the guitar to allow better access to the frets nearest the body. There are two common forms of cutaway, the Venetian and Florentine with the former being much more common. They are often played with a plectrum or flatpick and accordingly have a pickguard. A plectrum is simply a teardrop shaped bit of plastic although other materials are sometimes used. It is used to pick a string or strum multiple strings and gives a stronger and cleaner attack than a guitarist’s fingers resulting in a cleaner and louder sound.

4. Resonators

There has always been a quest to make louder guitars and so fill a larger space or to stand out in a band. Acoustic guitars are relatively quiet when compared to instruments such as drums and brass instruments and are easily lost in the “mix”. Before electronic amplification, mechanical methods were used to produce more volume. One such was the resonator design. A metal cone (or three in tri-cone designs) was placed in the body of the guitar with the bridge driving the cone. These are significantly louder and have a harsher, brighter tone much admired by devotees of early Blues music. Many of these are intended to be played on the players lap with a side or steel instead of conventional fretting. Pedal steel guitars are a further evolution that I will cover separately in the “electrics section”. The first resonators were seen in the 1920s but they are still made today for fans of older musical types. Some resonator guitars have all metal bodies with some of the finest being made of bell brass. If you have ever wondered about the strange chromed guitar on the cover of the Dire Straits album “Brothers in arms” then you will have seen and probably heard a resonator.

5. Lap steel guitars

As mentioned in the last section, resonator guitars are sometimes played on the player’s lap. This has been further developed in the lap steel and Hawaiian guitars which are normally unplayable in a conventional manner. Lap steels range from conventional looking guitars with square neck profiles to electric examples which are little more than a plank with strings and a pickup. Lap steels are always played with a slide. Rather than the player’s fingers forming chords by fretting a combination of notes, a slide or“steel” is used. This may be augmented by some fretting one or more notes with the fingers but that would be unusual as most music arranged for slide guitar is designed to be played on instruments where this is not practical. The slide or steel is generally a metal or glass tube that the player wears on one finger and slides up and down the strings to alter the pitch. This gives a smooth change of pitch that is quite characteristic. This was first done by Blues players who used a knife for the purpose. Later players (who presumably wanted to keep all their fingers attached) started using cut and smoothed parts of glass bottles for the job. One interesting point is that the length of the string is determined by the position of the slide and not by the frets. My own lap steel has frets that are only printed since the string will never come in to contact with them. They are often played with finger picks – essentially false fingernails used to pluck the string more firmly than would be possible with real fingernails – they are typically metal or hard plastic.

6. Travel guitars

Acoustic guitars are fairly bulky. If you go to any busy railway station, you will see people carrying or wearing guitars. In an attempt to make guitars more portable, travel guitars have been developed. Various systems have been tried from the very small bodied guitars such as the Martin Backpacker to guitars which can be disassembled like the SoloElite Dragonfly. Most of these win admiration for their novel design rather than their tone. The Martin Backpacker in particular has a disappointing sound considering that Martin is among the finest acoustic guitar makers in the world. Interestingly some guitars which would previously be described as parlour guitars are now being marketed as travel guitars. A parlour guitar is just a conventional acoustic guitar with a small body. I have a Tanglewood Baby that was marketed as a travel guitar. Happily, it is an exception to the rule that small bodied guitars have inferior tone. As the name suggests, it is a small bodied variant of a larger but similar guitar. The Baby has a “toppier” tone which is to say that the higher pitched overtones are dominant in the sound which I personally prefer.

7. Electro acoustics

These are guitars that are essentially acoustic guitars which have been fitted with a microphone to enable them to be amplified. Guitars of this type often have a small graphics equaliser built in to the body. It is also possible to retrofit a microphone in to a conventional true acoustic which popular kits such as the Fishman acoustic pickup. The microphone is normally mounted in the soundhole or at the base end of the body – the two mountings provide different tonal qualities and there is much debate over which is the better position. Guitars of this type suffer from feedback problems when played with high amplification – the soundboard vibrates from the amplified sound which is picked up by the microphone and sent to the amplifier which plays the sound which makes the soundboard vibrate… and so on until the sound dissolves in to a distorted howl. This feedback effect is often used in rock where solid body guitars predominate – the effect is much easier to control in solid body guitars.

Electric Guitars

Electric guitars are the mainstay of modern Rock, Blues, Funk and much pop. They range from electro-acoustic guitars to wonders of electronics. They use magnetic pickups to convert vibration in the string to a signal for an amplifier. Electric guitars are very quiet indeed when played unamplified with solid body guitars being effectively silent since they have no sound cavity to project the sound. Electric guitars are always steel strung and have a truss rod to counter the pull of the strings - except for some Rickenbackers which have two and some early Telecasters which had none. Most statements about guitars seem to have an "except" clause.

Conventional magnetic pickups have one pole per string – the strings have a steel core and the movement of the string through the magnetic field of the pickup creates a small current which is then sent to an amplifier and on to one or more loudspeakers.

8. Semi-acoustics, sometimes called archtops

These are guitars which are hollow bodied but have magnetic pickups. They may be similar in appearance to conventional acoustic guitars but generally have a thinner body. They very often have a classic appearance since the more avant-garde designs work less well – and the more avant-garde designers have generally favoured the solid bodied rock guitars. Classic examples of this type of guitar are the Epiphone Casino, the Gibson ES-335 (the ES stands for Electric Spanish) and the Rickenbacker 360. Technically, these guitars can be played acoustically since they are hollow bodied but the sound is too thin and quiet to be useable. They suffer from the same feedback issues as the electro acoustic designs. It was this problem that led to the development of the solid body guitar – a definite improvement on the previous solution of stuffing towels in to the hollow spaces of the guitar. These are the guitars most commonly used in Jazz. Their construction is similar to that of acoustic guitars.

9. Solidbody electric guitars

These are available in a bewildering variety of styles and colours. As a guitarist, I can confidently state that they all sound and feel different. To most non-guitarists, they all sound pretty similar. They all have the same basic design – a solid slab of wood for a body with one or more magnetic pickups. The differences between different models may be cosmetic or more fundamental.

Wood type

The type of wood affects the density of the guitar body and the acoustic properties. While solid body guitars do not project the vibration of the plucked string, the vibration travels within the body of the guitar and resonate giving complex overtones. Generally, the denser the body, the “darker” the tone. Guitars such as Gibson’s Les Paul models use Mahogany with a maple cap and have a characteristic dark tone when compared to guitars made of Ash or Alder which are much less dense woods. These woods are used on guitars such as Fender’s Stratocaster and Telecaster which have a brighter tone. It is always difficult to describe guitar tone as English (and probably other languages) lack the words required to capture the subtle differences. Denser, harder woods also give more sustain – the note takes longer to die away after being sounded. How desirable this is will depend on the style of music being played. The least dense guitar that I have played is the Danelectro U2 which is made primarily of Masonite, a material more commonly used for suitcases. This gives a remarkably bright jangly tone.

Pickups

There are three types of pickup reasonably commonly used on electric guitars: Single coil, humbucker and Piezoelectric. Some guitars have more than one type fitted to give a wider range of sounds. Pickup selector switches allow one or more pickups to be selected at the same time. Only the first two of these are magnetic pickups. These have a magnet per string (or a single large magnet on some cheaper models) wound with coils of wire which sit in the body under the strings. These coils of wire pick up the current generated by the ferrous string moving in the magnetic field created by the magnet. Single coil pickups are used to excellent effect on guitars such as the Telecaster and Stratocaster. They are generally paired with lower density woods. Single coil pickups have perhaps the most guitar-like of the tones available from magnetic pickups but they suffer from electrical interference. The Stratocaster is famous for its 50 or 60 Hz hum (depending on location) when no note is being played. The humbucker was developed to eliminate the hum. It does this by having paired couples of coils which are arranged to be out of phase to cancel out the interference. This works well but gives a different tonal response to the single coil – and a higher output which is much prized by rock guitarists. The thicker tone of the humbucker is generally paired with denser woods and classic humbucker equipped guitars include the Gibson Les Paul and Gibson SG (short for Solid Guitar). Some guitars which are intended to for heavy rock are equipped to allow up to 8 pickups to be used at once to give ludicrously high output levels. Piezo-electric pickups are quiet different. They are normally built in to the bridge of the guitar and use crystals to convert pressure (and accordingly vibration) in to voltage. The output of these crystals is very small and it is normally necessary to have active electronics built in to the guitar to convert the signal to a usable level. Piezo pickups give the most faithful reproduction of the vibrations occurring within the guitar. They are the least common type of pickup. There are also MIDI pickups but they are very rare. I will mention them again when I come to the future of the guitar.

The Whammy Bar / Vibrato / Tremolo

This is the handle like projection that you may have seen on electric guitars. The original purpose was to add a little vibrato to a played note or chord. They are not used so much these day except in heavy rock where a technique known as the Divebomb is used. The way that the whammy bar works is that it allows you to alter the tension on all the strings at once very rapidly. A little tug and the pitch swings up. A little push and the pitch drops. A Divebomb is a huge drop, sometimes making the strings go completely slack and hit the pickups with a bass thud. The first systems were the Fender 3 screw system and the Bigsby system. Both had disadvantages. The Fender system often caused the tuning of the guitar to drift. The Bigsby system was more stable but allowed less variation. Various refinements were tried with some success at improving both systems. The biggest advance was the Floyd Rose Tremolo which has the strings clamped at both the nut and the bridge giving excellent tuning stability. It is a floating tremolo which means that it can travel both up and down so it is both stable and highly variable. One common type of tremolo seen on modern guitars is the hard-tail tremolo where the pitch can be lowered but not raised beyond original pitch because the bridge is mounted flush to the body of the guitar. This is slightly cheaper to build and rather more stable.

The bridge and the mounting of the strings

Various approaches have been used to attach the strings to the body. Acoustic guitars use plastic pegs to hold the strings in to the body and a single bridge. Electric guitars have the strings going through holes in the bridge – in the case of some guitars such as the Telecaster, though the body of the guitar as well. While acoustic and classical guitars have a single bridge, electric guitars have three or six saddles that make up the bridge. These essentially are segments of the bridge that are individually adjustable to allow the intonation to be adjusted. A string that is in tune when played open (no note fretted) may be out of tune when played fretted at the 12th fret (one octave higher). By small adjustments to the saddle, the length of the string can be adjusted to give a good compromise so that the string isn’t far out of adjustment at any point on the neck. It has always struck me as strange that the most expensive custom made acoustic guitars don’t have any adjustment at all for this while the cheapest and nastiest electric guitar does.

Tone controls

The tone control of most guitars is classic 1950’s electronics. Essentially, the tone control allows you to bleed off some of the higher frequencies. Internally, it is simply a variable resistor (a rheostat) and a small capacitor.

Styling

For many guitarists, look is as important as function. The style of the guitar will have a lot to do with the sort of music that the guitarist is playing. Heavy Metal guitarists will want something in black with spiky bits. A blues player will want something more traditional. The most common designs are based around a few classics. The Telecaster is a guitar shaped slab with a single real cutaway. It has always been a popular shape and has recently enjoyed a return to fashion. The Stratocaster is the most copied shape of all with its wonderfully retro design that was intended to look futuristic in the 1950s. Instead it conjures up images of classic American cars. It is a design classic loved by many stars such as Jimmy Hendrix, Mark Knopfler, Eric Clapton and countless others. The Les Paul is a small bodied guitar, mercifully so as the thick mahogany body is very heavy. The classic versions of this body type are the flame top (so called because of the tiger striped grain on the maple cap) and the gold top. Again, this is a hugely popular shape that has been copied many times. Any number of heavy rockers have used them including Zakk Wylde with a striking black and white bullseye design. At least 70% of the guitars that you see in a shop will be based on these designs.

The future of guitars

Most guitars are essentially based on 1950’s technology but there are some interesting advances in the wind.

Gibson have built a Les Paul which has an Ethernet interface to connect directly to a network. Applications are so far limited but computers are increasing the recording solution of choice. It is yet to find a mass market.

MIDI pickups are now built in to some high end guitars and are available as a rather costly after market add-on. With the pickup and an electronic box of tricks, the guitar can output MIDI and with a synthesiser mimic a wide range of instruments including electronic and wind instruments.

Perhaps the most radical change is the modelling Guitar. “Line 6” produce the Variax range that have some very advanced digital signal processing (DSP) built in. The design hides this behind conventional controls so that the guitar appears like a guitar and not like the computer that it really is. The most striking visible difference is that there are no magnetic pickups. The pickups are actually piezoelectrics built in to the bridge. The signal from these is fed in to the DSP and converted in to very good copies of classic guitars. With the guitar selector knob and the pickup selector, you can select from an entire stable of classic guitars including some very rare acoustics. It is a remarkable bit of engineering.