Understand Your Guitar
A Deep Beginner’s Guide
I picked up a guitar for the first time about a year ago. Here’s how I have made sense of it.
Strings
A typical guitar has 6 fixed-length strings along its neck.
Each string has a different weight from the other strings. The thicker the string, the heavier it is. The strings are laid out in order of thickness, with the thickest string at the top when you hold the guitar. The strings are usually drawn as if you’re looking down on your guitar while it lies face-up on your lap. So the thinnest string is drawn at the top and thickest at the bottom. You can refer to each string by a number from 1 to 6, with 1 being the thinnest string and 6 being the thickest string.
Each string has a tension that you can adjust.
Sound
When you pluck a guitar string, it vibrates to produce sound. The sound has a fundamental frequency that is determined by the length, tension, and weight of the string:
The frequency (or pitch) increases with increasing tension (using the tuning knobs) or decreasing length (by pressing down on a string).
The sound produced by plucking a string also contains multiples of the fundamental frequency. These are called harmonics.
Frets
Frets are strips of metal laid out on the guitar neck (below the strings) perpendicular to the strings. You can refer to a fret by its position relative to the guitar head, starting at 1.
When you press down on a string anywhere on the guitar neck, and then pluck the string, the length of the vibrating string is shortened to the next fret towards the guitar body. Since the frequency of a vibrating string is inversely proportional to its length, the produced sound has a higher pitch compared to when the string is plucked without pressing down.
The frets get closer together as you go up the neck (up as in towards higher frequencies, in the direction of the guitar body). Every successive higher fret spacing is reduced by a factor of 2^(1/12). This means that the fundamental frequency at a fret is 2^(1/12) times higher than that at the next lower fret (towards the guitar head). And every 12 frets the fundamental frequency doubles. So the sounds produced at fret n and fret n+12 have the same harmonic frequencies and are, in that sense, equivalent. You can think of the fretboard as repeating every 12 frets with the sounds doubled in frequencies. Once you understand the fretboard up to the 12th fret, you understand an infinitely long fretboard.
Intervals
Why are the frets arranged to increase the sound frequency by a factor of 2^(1/12) between adjacent frets? Because that is precisely how musical notes are spaced out in frequency. A musical note has a frequency given by 2^(n/12) * 440 Hertz (where n is an integer).
The musical interval between two notes played on one guitar string can be expressed as the distance between the frets. For example, the note played on fret 7 is +5 away from the note played on fret 2 of the same string. This is equal to the number of note-hops to get from the fret 2 note to the fret 7 note when the notes are arranged in increasing order of frequency.
What about the interval between notes played on different strings? Since each string has an adjustable tension, you tune the tension on each string so that the notes played on the open strings are a chosen interval apart. In the standard tuning, each string is +5 away from the next thicker string, except for string 2 which is +4 away from string 3.
Note Names
When two notes are 12 apart, the interval is called an octave and the higher note is twice the frequency of the lower note. Notes that are an octave apart are in a sense equivalent (have the same harmonic frequencies) and are referred to by the same note name. So the 12 notes in an octave can be logically arranged in a note-circle. When you traverse the circle in a clockwise direction, the intervals increase by 1 between successive notes. In the counter-clockwise direction, the intervals decrease by 1.
A sharp suffix (♯) indicates a note +1 away from the indicated letter. A flat suffix (♭) denotes a -1 lower note. The reason the notes are named with a combination of 7 letters and sharps and flats rather than 12 letters has to do with how specific subsets of 7 notes form musical scales.
The frequency of a note is fully specified by the octave and the note name within the octave. A4, which is the note A in octave 4, has a frequency of 440 Hz. Middle C or C4 is the first note in octave 4. It is -9 away from A4 and has a frequency of 2^(-9/12) * 440 Hz or ~262 Hz.
In the standard tuning, strings 1 to 6 are tuned to E4, B3, G3, D3, A2, E2 respectively. This is consistent with the inter-string intervals mentioned before (each string being +5 away from the next thicker string, except for string 2 which is +4 away from string 3).
Note Repetition
You can play 72 possible notes on any span of 12 frets on a 6-string guitar. In the standard tuning, each note is repeated 6 times in such a span (once on each string, at possibly different octaves).
How do you find the 6 incarnations of a particular note in a span of 12 frets? Consider the note on string 6 at some fret n. Here are the positions of that same note (at possibly different octaves) within 6 frets on either side of fret n:
- string 6, fret n
- string 5, fret n-5: same octave
- string 4, fret n+2: 1 octave higher
- string 3, fret n-3: 1 octave higher
- string 2, fret n+5: 2 octaves higher
- string 1, fret n: 2 octaves higher
Here are the notes C, A, G, E, and D across the fretboard, following the above pattern. The order of the notes is chosen so that each pattern is obtained from the previous one by dragging it to the left until the second note from the guitar head is in the open position. This clearly illustrates how the note-repetition pattern repeats in a span of 12 frets.
Why are there repeated notes on a guitar? Why not just a single string guitar with 12, 24, or 36 frets to span 1, 2, or 3 octaves respectively? For a couple of reasons:
- Multiple strings allow you to play multiple notes simultaneously, in harmony.
- Repeated notes allow you to play all the notes in a melody on the same part of the guitar neck (across strings), instead of having to traverse the length of the neck.
Scales
Once you know how the musical notes are laid out across the fretboard, which ones do you play to make music?
You first choose a main note, called the root note. Then, you choose a subset of the notes at prescribed intervals from the root note. When these notes are played as a melody (i.e. one note at a time) or as chords (i.e. multiple notes simultaneously) they sound pleasing to the human ear. Such patterned-interval subsets of notes are called scales.
There are many different scales. The most commonly used ones are major, minor, and their pentatonic subsets.
Major Scale
You can play happy-sounding melodies using the notes in a major scale. There are 7 notes that follow a specific pattern of intervals from the root note. You can visualize the pattern as spokes that select 7 notes from the note-circle:
Imagine super-imposing the spokes on the note-circle. Rotate the spokes until the big green arrow points at the root note of your choice on the note-circle. Then the other green arrows point at the other notes in the major scale in the key of the root note. The order of the notes is clockwise from the root note. For example, below are the notes in a few commonly used major scales.
If you start at the root note on any of strings 3 to 6, you can play all the notes in one octave of the scale, on the same part of the neck, using the following patterns:
The pattern has the same 3 strings structure for the root note on any string, except that when playing on strings 2 and 1 the pattern is shifted right by 1 (due to string 2 being +4 away from string 3, instead of +5, in the standard tuning).
Major Pentatonic Scale
The major pentatonic scale is a 5-note subset of the major scale that you can use to improvise or solo. It is constructed by removing the 4th and 7th notes from a major scale. Here’s the major pentatonic spoke spokes diagram:
Below are the notes in a few commonly used major pentatonic scales.
If you start at the root note on any of strings 3 to 6, you can play all the notes in one octave of the scale, on the same part of the neck, using the following patterns:
The pattern has the same 3 strings structure for the root note on any string, except that when playing on strings 2 and 1 the pattern is shifted right by 1 (due to string 2 being +4 away from string 3, instead of +5, in the standard tuning).
Minor Scale
You can play sad-sounding melodies using the notes in a minor scale. There are 7 notes that follow a pattern of intervals from the root note represented by the following spokes diagram:
How does this pattern of intervals compare to the major scale? You can think of the minor scale as derived from the major scale by flattening the 3rd, 6th, and 7th notes in the major scale.
Below are the notes in a few commonly used minor scales.
Note that the notes in the A minor scale are exactly the same as the notes in the C major scale. That is not a coincidence. A minor scale in a root note is equivalent to a major scale in a +3 root note. You can visualize this by using the same spokes diagram to represent both the minor and major scales, except using different starting points for the root notes:
If you start at the root note on any of strings 3 to 6, you can play all the notes in one octave of the scale, on the same part of the neck, using the following patterns:
The pattern has the same structure for each root note, except that when played on string 2 and string 1 the pattern is shifted right by 1 (due to string 2 being +4 away from string 3, instead of +5, in the standard tuning).
Minor Pentatonic Scale
The minor pentatonic scale is a 5-note subset of the minor scale that you can use to improvise or solo, just like the major pentatonic scale. It is constructed by removing the 2nd and 6th notes from the minor scale:
Below are the notes in a few commonly used minor pentatonic scales.
Here are the patterns to play the minor pentatonic scale when you know where the root note is:
When the root note is on strings 1, 4, 5, or 6, the pattern is the same box shape extending one string up and/or down from the root note string. When the root note is on strings 2 or 3, the pattern is a house-shaped one (inverted for string 2).
Unified Spokes Diagram
You can visualize the major and minor scales, and their pentatonic subsets using a unified spokes diagram. The root notes for the minor and major versions are marked separately. The dashed-line spokes are the notes to be omitted from the pentatonic scales.
Chords
A chord is a set of notes with specific intervals, played simultaneously. You play chords to add rhythm and harmony to your music.
Major Chords
There is a major chord associated with a major scale. It consists of the 1st, 3rd, and 5th notes from the major scale, played simultaneously, with some notes possibly repeated at different octaves. The intervals from the root note are: root, +4, +7
The commonly used major chords are C, A, G, E, and D. Each of them can be played within the first three frets using at least one open string. This is known as the open position. Here are the shapes:
Note the connection between the root notes in the open chord shapes and how any note is repeated across the strings in a span of 12 frets. The C-shape connects a note on string 2 to string 5 (since those strings play the rot C note in the open C chord). Then the A-shape connects string 5 to string 3, the G-shape connects string 3 to strings 1 and 6, the E-shape connects strings 1 and 6 to string 4, and finally the D-shape connects string 4 to string 2. You can use the mnemonic CAGED to help remember which chord shape to invoke to find the previous or next root note on the fretboard.
Each of the open chord shapes can be transposed to higher frets. For example, if the C chord is played 2 frets higher (with a finger pressing all strings on the second fret), then each note will be shifted by +2, leading to the sound of a D chord using the shape of a C chord. Such transposed chord shapes are called bar chords (so named because they require you to bar multiple strings on a fret).
You can use bar chords to play every major chord using one of the open chord shapes and barring the appropriate fret.
Specifically, you can play chords that don’t have an open position in the standard tuning e.g. B and F.
Minor Chords
There is a minor chord associated with a minor scale. It consists of the 1st, 3rd, and 5th notes from the minor scale, played simultaneously, with some notes possibly repeated. The intervals from the root note are: root, +3, +7.
You can derive a minor chord from a major chord by flattening the +4 notes in the major chord to +3 notes.
The commonly used minor chords are Am, Dm, and Em. Each of them can be played in the open position (just like the C, A, G, E, and D major chords). Here are the shapes:
Bar chords work for minor chords, just like they do for major chords, by barring the appropriate fret and using the appropriate chord shape.
For example, here are the Bm (Am-shape, +2), Cm (Am-shape, +3), Fm (Em-shape, +1), and Gm (Em-shape, +3) bar chords:
Chords In A Key
If you know that a piece of music is in a particular scale, you can choose associated chords to harmonize well with the melody. Which chords? Those that are made up of notes from the scale.
In a major scale, the harmonizing chords are the major chords for the 1st, 4th, and 5th notes and the minor chords for the 2nd, 3rd, and 6th notes. For example, if a song is in the G major scale, a chord progression involving the major chords G, C, D, and the minor chords Am, Bm, Em will sound good.
In a minor scale, the harmonizing chords are the minor chords for the 1st, 4th, and 5th notes and the major chords for the 3rd, 6th, and 7th notes. For example, if a melody is in A minor, then choose a chord progression involving the minor chords Am, Dm, Em and the major chords C, F, G.
Power Chords
A power chord consists of the 1st and 5th (+7) notes in a major scale. In fact, the associated minor scale has the same 1st and 5th notes, so a power chord can be played in place of either a major or a minor chord. The intervals between the notes are: root, +7.
Here are the open-position power chords that can be played with one finger:
Here are the 2-finger movable power chords that can be played with the root note on any of strings 2 to 6:
Here are the 3-finger movable power chords that double up on the root note and can be played on any of strings 3 to 6:
Summary
Here are the main ideas encapsulated in 3 cheat sheets.
