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Intervals are how musicians measure the distance between notes — and the key to why chords and scales sound the way they do. You'll learn to count in semitones, name the intervals that come from the major scale (the major and minor seconds through sevenths, the perfect fourth and fifth, and the tritone), see how the major and minor pentatonic scales and the dominant chord are each built from a simple interval formula, and pick up a count-by-fives trick for measuring any two notes on the neck. Nothing to memorize — just the vocabulary you'll lean on for the rest of the course.
What follows is this lesson’s section of the Course Guide — you can read it here or in the full guide →
Intervals are the way that musicians measure distances between notes, and they are helpful because they correspond closely to how notes sound in relationship to scales and chords.
An interval can be reduced to the number of frets between two notes on one string, and we can define scales and chords by the intervals between their notes. The music theory term for a one-fret distance is a semitone (also known as a half-step).
A 12-semitone distance is one octave, and just as there are 12 notes in the chromatic scale, there are 12 distinct intervals that repeat after reaching a distance of 12 semitones. If you ever come across an interval of more than 12 semitones, you can subtract 12 from the number as many times as needed to get a distance in the range from 1 to 12.
Unless otherwise specified, an interval name is measured going up in pitch from a reference note to a target note. The reference note is usually the root of a chord or scale.
Here are the 12 intervals, their shorthand labels, and their official names:
| Semitones | Abbreviation | Interval name |
|---|---|---|
| 0 | R | root / unison |
| 1 | m2 | minor 2nd |
| 2 | M2 | major 2nd |
| 3 | m3 | minor 3rd |
| 4 | M3 | major 3rd |
| 5 | P4 | perfect 4th |
| 6 | #4/♭5 | tritone |
| 7 | P5 | perfect 5th |
| 8 | m6 | minor 6th |
| 9 | M6 | major 6th |
| 10 | m7 | minor 7th |
| 11 | M7 | major 7th |
| 12 | P8 | octave |
We can calculate the interval between two notes by counting in fives as we move between strings: +5 for each string change if we are moving toward the high E string, and -5 if we are moving toward the low E string. If we move between the G and B strings, we need to move diagonally to accommodate the warp. Then we count frets horizontally, adding +1 for each fret moving toward the bridge, and -1 for each fret moving toward the nut.
Once we have an initial distance measurement, we must ensure it’s in the range from 1-12. If the number is negative, keep adding 12 to it until it is positive. If it is greater than 12, keep subtracting 12 from it until it is less than 12. Then, you can use the above table to convert the semitone distance into an interval name.
There is a more detailed video about this available on YouTube if you’d like to see more examples, but this simple version should be sufficient to follow along with this course.
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