The distance between the pitches of two notes is known as an interval, and is measured in semitones. On the guitar, 1 fret = 1 semitone (or half-step), 2 frets = 1 whole tone (or whole-step). Note that this tutorial just deals with intervals of less than 1 octave (12 semitones); there'll be another tutorial at a later date which covers bigger intervals.
When referring to intervals, the interval can be given a name based upon the distance between the notes within a scale. For example, using the C major scale:
| C è C | 0 semitones | Unison (or Perfect Unison) | |
| C è D | 2 semitone | Major 2nd | |
| C è E | 4 semitones | Major 3rd | |
| C è F | 5 semitones | Perfect 4th | |
| C è G | 7 semitones | Perfect 5th | |
| C è A | 9 semitones | Major 6th | |
| C è B | 11 semitones | Major 7th | |
| C è C | 12 semitones | Perfect Octave | |
Naming Convention:
| Interval Name | Size (semitones) | Example | |
|---|---|---|---|
| Unison Diminished 2nd |
0 | C è C C è Dbb |
|
| Minor 2nd Augmented Unison |
1 | C è Db C è C# |
|
| Major 2nd Diminished 3rd |
2 | C è D C è Ebb |
|
| Minor 3rd Augmented 2nd |
3 | C è Eb C è D# |
|
| Major 3rd Diminished 4th |
4 | C è E C è Fb |
|
| Perfect 4th Augmented 3rd |
5 | C è F C è E# |
|
| Augmented 4th Diminished 5th |
6 | C è F# C è Gb |
|
| Perfect 5th Diminished 6th |
7 | C è G C è Abb |
|
| Minor 6th Augmented 5th |
8 | C è Ab C è G# |
|
| Major 6th Diminished 7th |
9 | C è A C è Bbb |
|
| Minor 7th Augmented 6th |
10 | C è Bb C è A# |
|
| Major 7th Diminished Octave |
11 | C è B C è Cb |
|
| Perfect Octave Augmented 7th |
12 | C è C C è B# |
|
An interval can be 'harmonic' or 'melodic' - when two notes are played together then the interval between them is said to be harmonic; a melodic interval occurs between two notes played in succession:
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Each interval, whether harmonic or melodic, has its own unique sound. Some intervals, such as a perfect fifth, or octave have a fairly consonant (or resolved) sound. Others, such as a minor 2nd or diminished 5th have a much more dissonant (or unresolved) sound. The degree of consonance/dissonance is particular to the size of the interval, and not to its notes. For example, perfect 5th between C and G sounds just as resolved as an interval of a perfect fifth between A and E.
Training you ear to recognise the sound of each interval is a vital skill. Spend time learning the names of intervals, and understand how they relate to the parent major scale. More importantly, put the theory into practise: as part of your daily practise routine, spend time playing and listening to intervals - in time you will come to recognise them upon first hearing. It will seem like hard work at first, but it is a very worthwhile investment of your time so persevere.
Guitarists might also find it useful to refer to this chart to see how intervals are laid out on the fingervboard.
More about ear-training in a later tutorial, but in the meantime...good luck.
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