One of the most popular musical instruments of the past century, the electric guitar arguably redefined the meaning of the term popular music. It is obviously based on an already existing instrument – acoustic and classical guitars having existed in some form for hundreds of years.
However, unlike acoustic instruments, which rely on a resonant box to produce their sound, the electric guitar is almost silent – without amplification, it produces almost no sound!
However, when plugged into an amplifier, the true nature of the electric guitar becomes apparent – it takes on a completely different character, with sustain unlike any acoustic instrument, and with volume that can completely fill a venue.
It becomes one of the most versatile instruments available to us, with various character-altering pedals and effects, that give the electric guitar a range of sounds available that is only rivaled by extremely complex synthesizers.
Fundamentally, an electric guitar works through electrical signals. Unlike an acoustic instrument’s resonant box, which requires a level of craftsmanship to be able to create, the electric guitar’s sound-making components are a relatively crude affair, requiring just a few simple pieces soldered together in a circuit.
Whereas an acoustic guitar’s soundbox requires a level of skill that simply must be learned and practised to craft, an electric guitar’s circuitry could be soldered together even by an untrained hand in under an hour.
However, that’s only a part of the sound-making system – an electric guitar requires an amplifier, which is the key part of the sound. Indeed, amplification is arguably the very point behind the creation of the electric guitar, as it lets the instrument be played at much, much louder volumes than is possible with acoustic instruments.
At a certain volume threshold, the acoustic guitar’s soundbox will start to resonate against itself, creating a feedback loop and a horrible, uncontrollable screeching sound.
Feedback of this sort is a much smaller issue when it comes to the electric guitar – as the sound comes not directly from the guitar itself, but instead from an external device that amplifies the electrical signal coming from the guitar.
All sound is vibration – absolutely all of it. When a guitar string is plucked, it vibrates back and forth at a certain rate. This is measured in Hertz (Hz) – a sound that has a value of 440Hz, for example (an A note) is vibrating back and forth 440 times per second.
If you could see a speaker playing this note in slow motion, you would clearly see it vibrating back and forth at a rate of 440 times per second. Likewise, a guitar string plucked to play an A note would (depending on the exact pitch played) vibrate at a rate that is a multiple of 440 times per second – I.e., an A note an octave higher would vibrate at 880 times per second.
So, a guitar string is plucked, and it vibrates, making a note. In an acoustic guitar, the design of the box that is the body of the guitar dictates a lot about how well we can hear this vibration, and accordingly, the sound that the guitar makes. However, we know that an electric guitar works differently – so how does an electric guitar make its sound?
You’ve likely noticed something on electric guitars that doesn’t (mostly) exist on acoustic guitars – the pickups. These are embedded into the front of the guitar, underneath the strings.
Some are larger than others, some are smaller, and there are many different designs – as well as many different ways of connecting a set of pickups together. However, they are all based on the same fundamental principle.
A coil of thin copper wire is spun around a bar magnet, up to thousands of winds. Connected to the output jack of the guitar, this works on a similar principle to an electric motor in reverse.
Whereas an electric motor (which is also essentially a coil of wire wrapped around a magnet) takes electrical power and creates motion, the guitar pickup takes motion – in this case, the motion of the string next to it – and, through electromagnetic induction, outputs electric power.
Because the amount of electrical power output is directly related to the vibration created by a string – and because the amount it vibrates changes depending on whether our fingers have shortened the vibrating section of the string by fretting notes – the amount of electrical power output is directly related to the notes we are playing.
The final stage in the signal chain is the amplifier and speaker. The electrical signal coming from the guitar is extremely weak, and without something to make it louder is useless to us. This is the fundamental role of the amplifier.
It takes a weak signal such as this, and makes it louder – a lot louder. A powerful amplifier can take the guitar, which is practically silent when unamplified, and make it loud enough to deafen an entire concert hall.
To play at these volumes with an acoustic instrument could well make it vibrate and feed back in a deeply unpleasant manner – but for a well set-up electric guitar, earth-shattering volume is par for the course.
Of course, the amplifier cannot do this all on its own – it needs a loudspeaker. Without the amplifier to boost the signal, the electric guitar could not output a signal that would activate a speaker – absolutely nothing would be heard.
However, the amplifier can boost the signal and push that boosted signal through these speakers, turning a nearly silent instrument into one of the loudest instruments of all.
With these components, the electric guitar has a nearly limitless range of volume, being able to be played silently, or loud enough to fill the largest arenas.
The way an electric guitar (and, by extension, an electric bass) works is unlike most other instruments. By relying on electrical signals to transmit the sound, rather than creating the sound by vibrating parts of itself enough to be heard, it allows for levels of volume that other instruments would find difficult or impossible to achieve!