Ever wondered how your guitar tuner works? Or why some tuners are more accurate than others? Well stay er…..tuned. Today we’re going to delve into the world of guitar tuners and explain how tuners work, and how pitch is measured.
The Short Answer
Guitar tuners detect a signal through a sensor, microphone, or instrument cable. The signal is amplified before being converted from analogue to digital and pitch detection occurring. As sound waves change over time, tuners process a series of sound waves and then calculate an average, which is then displayed visually in comparison to the nearest relative note of either the chromatic scale (chromatic tuners) or notes of the guitar in standard tuning (non-chromatic tuners).
While the information above is a good summary, there’s actually a lot more to guitar tuners, including a lot more about how they work, the different types available and which are the most reliable. So, if that sounds interesting, we’ve got you covered below.
[The Long Answer] How Guitar Tuners Work
How pitch is measured
To really understand how guitar tuners work, first we need to understand how pitch is measured, and also a little about how sound is created.
To start with, all sound is a series of vibrations.
These vibrations create compression waves (aka sound waves) that travel through the air creating different areas of pressure known as compressions (the air particles are compressed together) and rarefactions (the air particles are spread apart).
As sound waves travel through the air they interact with the air molecules around them, causing objects to resonate e.g. Something vibrating that causes another object to vibrate at the same frequency.
An example of this is our eardrums, which as part of a process of hearing eventually through the transfer of vibrations causes the tiny hairs within the cochlea (inner ear) to vibrate, creating an electrical signal that our brain interprets as sound.
How a note sounds, including its volume and pitch is determined by the attributes of the sound wave.
The height of the sound wave determines amplitude (volume) and frequency e.g. number of sound waves within a set period (e.g. per second) determines pitch.
This means the closer the sound waves are the higher the pitch of the note. Alternatively, the further apart the sound waves are, the lower the pitch of the note.
The frequency of a note is measured in Hertz (Hz). What this really means is the number of completed sound waves per second that occur when a note is played.
Middle C on a keyboard has a frequency of 262Hz. This means 262 sound waves are completed per second when middle C is played.
Below are the frequencies of the open strings of a guitar when tuned to concert pitch. For frequencies exceeding 1000 we can use the unit Kilohertz (kHz). 1kHz is equal to 1000 Hz.
|6th String (Low E)||82.4Hz|
|5th String (A)||110.6Hz|
|4th String (D)||146.8Hz|
|3rd String (G)||196.0Hz|
|2nd String (B)||246.9Hz|
|1st String (high E)||329.6Hz|
When measuring smaller increments of pitch we refer to Cents. But if you are wondering how many cents there are to a Hz, it’s not that simple.
We know that notes relate to frequency, but, interestingly, when we double the frequency of a note the human ear recognizes it as the same note, it’s just one (or more) octaves higher.
For example, middle C is 262Hz. C in the next highest octave (C5) is approximately double the frequency at 523.25Hz, and in the next highest (C6) 1046.50hz.
This means the increase in frequency as a note increases in pitch is not linear, but exponential. This is essentially how octaves work.Wondering what C5 and C6 means? The number represents the octave. Middle C for example is C4.
The 12 semitones that make up the individual notes of an octave (C, C#, D, D#, E, F, F#, G, G#, A, A#, B) that lie between 262Hz (middle C or C4) and 524Hz (C5) are divided into 12 equal pitches, known as 12 tone equal temperament.
The frequency of the notes however, change logarithmically because the frequency doubles whenever we play a note in the next highest octave. This means the number of cents in a Hz increases exponentially.
If this is starting to feel overly technical (I just wanted to know how a tuner works! And now my brain is melting) don’t worry, digital tuners do these calculations for us.
Types of tuners, and how they work
A guitar tuner in its simplest form detects a signal and using pitch detection establishes the frequency of the signal. It processes this information, converts it to its current pitch and then displays the information on a visual display. The guitarist then raises or lowers the pitch of the string by adjusting the tension of the string.
The display responds showing how close to correct pitch the note is after being raised or lowered.
Depending on the type of tuner, or the settings available on your tuner, it may show you the nearest relative note while tuning (chromatic), or just the notes of the guitar in standard tuning: E, A, D, G, B, and E.
To do all of these things, the initial signal must first be amplified, converted to digital and then output on the display. Each of these steps is covered in a little more detail below.
One of the challenges involved in designing a tuner is the relatively weak signal a guitar provides.
Because of this the signal must first be amplified (increased in voltage and power) using a preamp so the initial weak signal can be processed, without increasing the signal-to-noise ratio (SNR).
This results in an amplified, cleaner signal for your tuner to process.
Pitch Detection and Processing
The analogue sound waves (remember we talked about sound waves at the beginning of this article) are recorded at specific intervals and this information is then converted to a value in the form of a number by an analogue to digital converter (ADC).
The waveform is measured against time by the device’s processor to establish the frequency and determine pitch.
However, sound waves change over time, so to counter this problem tuners process a number of sound waves and then calculate an average.
Extracting the fundamental
When you play a note on any musical instrument, the main frequency you hear is the fundamental. But, additional frequencies are also produced.
The additional frequencies produced depend on the characteristics of the instrument. In the case of the guitar the strings play a role e.g. the mass of the string and vibrating length e.g. where you fret the string.
The fundamental is the lowest of the frequencies produced and defines the pitch of the note. The additional frequencies produced are called ‘overtones‘ and they are what gives an instrument its timbre. This is why a guitar, despite playing the same note sounds different to a violin for example.
The tuner has to separate the additional overtones to accurately detect pitch. Notes of lower frequency are typically more difficult to extract the fundamental from, as the lower the note the less separation between frequencies.
The fundamental is extracted using a type of filtering based on an algorithm that understands the relationship between the fundamental and the overtones produced. For example the harmonic series are overtones that are an integer of the fundamental.
The strobe tuner (which we’ll discuss below) uses a spectrum analyzer for this purpose.
Lastly the pitch detected is analyzed and converted to a value.
This number is then used to display the pitch of the note compared to the pitch of the note if it were in tune, by utilizing a digital display or a physical needle.
Needle displays show the note as being in tune when the needle is at a 90 degree angle. Digital displays often show a graphical representation of a needle and may show additional information including the note letter, how many cents the note is out of tune and other information including battery life.
Now that we know how tuners work, let’s learn more about the different types of tuners.
While Strobe tuners have been around since the 30s, and are highly-accurate, due to their fairly fragile nature and lack of portability (until recently at least) they are less common and tend to be expensive.
New handheld strobe tuners are now available, but these also tend to be more expensive than most of the competition, and guitarists tend to love them or hate them.
How do they work?
Strobe tuners work differently to other guitar tuners, which is why they are represented here on their own. They utilize a strobe light that is powered by the instrument (using a microphone or TRS input jack) to flash at the same frequency of the note being played.
This means if your 3rd string (G) was in perfect tune, the strobe would flash 196 times per second, the frequency e.g. the number of completed sound waves per second that results in the note G.
The frequency of light is then compared visually against a reference pattern marked on a spinning disc that is configured to the correct frequency.
When the frequency of the note matches the pattern on the spinning disc the image appears completely still. If not in perfect tune the image appears to jump around.
Strobe tuners are very accurate, up to 1/10000th of a semitone. To put that into perspective, that’s 1/1000th of a fret on your guitar!
The example of the woman running at the beginning of the video below demonstrates how strobe tuners work and why they are so accurate.
Tuning Forks, Pitch Pipes and Reference Notes
As strobe tuners were not really an option for most guitarists and portable digital tuners were yet to grace our guitar cases guitarists were forced to rely on other instruments, tuning forks or pitch pipes to provide a reference note to tune to.
The tuning fork has been around since the 1700s. It’s a two pronged fork that when struck resonates at a constant pitch that can then be used as a reference point for the guitarist.
When one string is in tune the guitarist can then tune the rest of the strings by knowing the intervals between the strings.
Portable Guitar Tuners and how they work
The Korg WT-10
It wasn’t until 1975 that anything remotely like the guitar tuners we have now were to become available when Korg developed the first portable, battery powered tuner, the Korg WT-10.
The Korg WT-10 was the first handheld instrument tuner, and utilized a needle meter to display pitch accuracy. The Korg WT-10 also featured a chromatic dial that had to be turned manually to the note you were tuning to.
You can see an example of the Korg WT-10 in the video below:
8 years later In 1983 Boss released the Boss TU-12, the first automatic chromatic tuner e.g. it automatically detected the nearest relative note and was accurate to within 1/100th of a semitone, in other words it’s accuracy was better than the human ear could detect.
Modern Guitar Tuners
Guitar tuners have come a long way since 1975 and more primitive tuners such as pitch pipes and tuning forks, while still around (many classical musicians still tune by ear), have largely gone the way of the dinosaur.
Dedicated guitar tuners are now designed for maximum portability, from compact, self-contained units to pedal tuners to smartphone tuning apps to light-weight clip on tuners that live on your guitar’s headstock. New tuners even offer polyphonic tuning, meaning they can detect the pitch of a chord.
Modern guitar tuners are most commonly powered by button cells aka watch batteries, Lithium rechargeable batteries that utilize a USB connection to recharge or are powered by AC power.
The most common types are:
- Handheld tuners
- These are dedicated tuners such as the Boss TU-12 and feature a microphone less accurate and/or ¼ instrument input jack.
- Clip-on Tuners
- This type of tuner clips onto the headstock of your guitar and detects the frequency of vibrations produced by the guitar.
- Sound hole tuners
As the name suggests, soundhole tuners are dedicated acoustic guitar tuners that are set on the inside edge of the soundhole of your guitar.
- Pedal Tuners
With regard to form pedal tuners are much like any other pedal, except they are a tuner. The guitar plugs directly in using a ¼” instrument cable.
- Smartphone Apps
Most smartphones are capable of detecting pitch using either an onboard microphone or by direct line and processing this information using the hardware already built into the phone.
*Many tuners also combine both a microphone and an instrument jack.
Clip on Tuners
Clip on tuners have become incredibly popular, and for good reason. They are a lightweight option that don’t use up a lot of battery power and can be used to tune your guitar even in a noisy environment, such as in a live setting.
While some clip on tuners utilize both a microphone and sensor unit, in most cases clip on tuners work by detecting the vibrations imparted on the guitar itself due to the frequency of the note being played, much like a piezo pickup works. In fact clip on tuners utilize Piezo crystals to detect changes in pressure caused by vibrations.
The frequency is then processed by the tuners on board circuitry and the relative accuracy of the note in comparison to the correct pitch is displayed on screen.
As can be seen in the image below, the D string (4th string) is too high by 7 cents according to the clip on tuner.
The most popular clip on tuner would arguably be the Snark ST-2, and despite clip on tuners not always enjoying the best reputation in terms of pitch accuracy, they often perform admirably against other tuners, as can be seen in the clip below.
Sound hole Tuners
Another reasonably new type of tuner, soundhole tuners work in much the same way as a clip on tuner but less visible for those who prefer not to obscure the manufacturer’s mark on your headstock.
Sound hole tuners mount inside the sound hole and as a result are only suitable for acoustic instruments, including acoustic guitar and ukulele.
This type of pickup usually features a highly visible display and simple controls, as they are required to be compact and unobtrusive.
While sound hole tuners also detect vibrations, one of the issues that can arise when using one is where they are situated on the guitar. The soundboard of an acoustic guitar is designed to move, in essence the vibrations from the strings are transferred through the bridge to the soundboard, but sound boards can also resonate from ambient noise, and when this occurs a sound hole pickup may detect vibrations not caused by the guitar they are installed upon.
Another common complaint is inaccuracy when tuning the low E string (you can read first-hand accounts of this here), although this depends on the brand. The Planet Waves NS Micro sound hole tuner is well reviewed and appears to suffer less from ambient noise.
Boss were the first company to introduce pedal tuners to the world (the Boss TU-2), but were apprehensive as they were unsure if there was sufficient demand. They released the pedal tuner in 1998 and the rest, as they say, is history.
One of the benefits of the TU-2 was that it allowed the guitar to be muted while tuning. This allowed the guitarist to tune in silence, and also meant as the microphone was not engaged the tuner did not detect external noise and make tuning more difficult.
Pedal tuners remain popular for live performance, and as this was their intended purpose the visual displays are often purposefully bright to stand out on dark stages.
Many guitarists now use clip on tuners, as they are arguably even more portable but for guitarists who utilize pedals, pedal tuners are a great option.
One of the more recent innovations in the tuning world are tuning apps. While none enjoy a stellar reputation, the iStroboesoft from Peterson Tuners (the same company who manufactured the strobe tuner referenced at the beginning of this article). Peterson claims the iStrobesoft tuner is accurate to within 1/10 of a cent, making it the most accurate tuning app available.
Other options I have used in the past include GuitarTuna which, if paying for the professional version, includes a huge number of open tunings, step down tunings, and other features. Aside from guitartuna, if you purchase the Ultimate Guitar app, under tools a chromatic tuner is included.
Smartphone apps normally utilize an onboard microphone rather than TRS cable for pitch detection. Microphone tuners can work well but are subject to outside noise, so are not practical in a live setting. They work by utilizing a microphone to detect sound waves.
In wrapping things up, I quickly wanted to mention polyphonic tuners, and tuners that offer polyphonic tuning. This is another relatively modern technology that detects the pitch of individual strings when a chord is strummed.
The TC Electronic PolyTune, is perhaps the most well-known polyphonic tuner and also offers chromatic and strobe tuning.
Generally this kind of tuner offers all the advantages of non polyphonic tuners, while also allowing the guitarist to quickly check their tuning by simply strumming a chord. This offers a much faster option for tuning, while still providing a fall back in the form of a chromatic tuning option.
Hopefully you now understand how a guitar tuner works, the different options available, which tuners are the most accurate and how pitch is detected and the units used to measure it.
While advancements will continue to be made, modern tuners are highly accurate. In most cases provided you purchase a tuner that has at least some brand recognition e.g. Boss, Korg, Peterson, TC electronic, Snark, you won’t run into many problems. For the sheer sake of convenience, definitely consider a clip on tuner, they’re popular for a reason after all and despite their often low price and a reliable option.