Musical Theory on Guitar: Intervals

Introduction

“This lesson will cover the concept of intervals. It will contain much terminology that will probably bore the advanced player while confusing the beginning player. The important thing is to associate a sound with each term. If it doesn't make sense now, hold on to this page - after a few more lessons, it probably will.”

What Intervals are

Distances between notes have certain names and arrangements. Those names are called intervals.

Why Intervals are Important

When trying to understand how particular notes will sound good together, whether melodically (in succession) or harmonically (simultaneous) i.e. in a scale, riff, chord, power chord, etc… you’ll need intervals to govern the rules. In other words, knowledge of intervals will help you understand how to compose, transpose, shift or simply follow scales, how to compose chords and how are they named, how to create your own chords and name them, and how to check if a chord fits a scale.

Intervals within one octave

As said before an interval is simply the distance between two notes. If we play one note after the other, the notes form a "melodic interval." When we play the notes together, they form a "harmonic interval." If the two notes are the same, we refer to the interval as a ”unison." The smallest distance above a unison is a "half step" (which, as we shall see below, is also called a minor second interval). Any notes played on the guitar on the same string separated by one fret are a half step apart (semitone). If they are separated by two frets, they are a whole step (or major second) apart. Notes separated by 12 half steps (semitones) make up an Octave (octaves have been explained in the previous lesson: bare Basics). On any one string on a guitar, an octave is made up of two notes exactly twelve frets apart. The scale made by playing the notes on every fret in an octave notes is a "chromatic" scale.

There are twelve distinct notes on most western instruments (on Oriental instruments such as Aud we have 24 distinct notes). We refer to the intervals within one octave as seconds, thirds, fourths, fifths, sixths, and sevenths. Unisons, fourth, fifths, and octaves are called "perfect" intervals. Seconds, thirds, sixths and sevenths can be either "major" or "minor," with the "major" interval being a half step greater than the minor interval. Between the perfect fourth and the perfect fifth is an interval called the "tri-tone," which has the same distance as three whole steps.

Below is a chart of the different intervals within one octave and the amount of half and whole steps that make up that interval.

Intervals on the Guitar Strings

The diagram below shows how to play these intervals on the guitar. Note that the diagram shows two ways to play each interval.

R = Root
mi = minor
Ma = major
p = perfect
TT = tri-tone
Oct = octave

First play the root, and then the other note marked with the interval. The interval refers to the distance between the root and the second note. Play the notes first as a melodic interval, both ascending and descending, and then (unless the notes are on the same string) as a harmonic interval. The point here is to demonstrate the sound of the interval. However, you should eventually find good fingerings to play each melodic and harmonic interval within one octave.

Diminished, Augmented, Flat And Sharp Intervals

A "diminished" interval is always a half step lower than a minor or perfect interval. Thus, a diminished 7th is the same as a major 6th. A diminished fifth is the same as a tri-tone. An "augmented" interval is always one half step higher than a major or perfect interval. An augmented 5th is the same as a minor 6th, and an augmented 4th is the same as a tri-tone. Note that all diminished and augmented intervals will be equal to another interval. The terms augmented or diminished are usually used when the interval is different from one would expect from the type of chord or the key.

"Flat" (or "b") or "sharp" (or "#") intervals are other common terms used to denote intervals. A flat interval is either a minor or diminished interval; it is used to identify an interval a half step lower than one would expect from the chord type or key. A b7 (flat 7^th) will usually mean a minor 7th. Sharps are usually augmented intervals but sometimes can be major intervals, and are used to identify an interval one half step higher than one would expect. A #6 is often a major 6 interval in a minor chord or key, which ordinarily contains a minor 6. A tri-tone is often called a b5 or a #4. –You didn’t understand this paragraph? Don’t worry, forget about it and keep reading.

Intervals Greater Than One Octave

The number sequence continues beyond the octave in a similar fashion. A 9th is the same as a 2nd but one octave higher. An 11th is the same as a 4th + one octave, and a 13th is the same as a 6th + one octave. These terms are mostly used for extended seventh chords. The terms 10th, 12th, and 14th are not usually used for reasons that will become clear when we discuss chords.

Inversions

When you descend (ie go backwards) from the root (say A) to an interval of a fourth (so it’s A>G#>G>F#>F>”E”), the note (E) will be an octave below the fifth (also E). Thus the "inversion" of a perfect fourth is a perfect fifth.

In other words:

-- D# -- E -- F -- F# -- G – G# --A-- A# -- B -- C -- C# -- D -- D# -- E --

-----------|--------------------------------|---------------------------------------------|---

                       Backward 4th Interval.          Root.                       Perfect 5th Interval.

The rules about inversions are:

a.      if you add up the interval numbers of an interval and it's inversion, the total is always 9

b.      the inversion of a major interval will always be a minor interval, and vice versa

c.      the inversion of an augmented interval is always a diminished interval, and vice versa

d.      the inversions of perfect intervals are always perfect

The use of inversions will get clearer when the “circle of fourths and fifths” is discussed. Keep in mind that inversions are different that chord inversions. Chord inversions will be discussed in the chords theory lesson.

Ear training

It is important to be able to distinguish different intervals by ear. Practice the intervals all over the neck. Play intervals at random, and try to identify them. Some intervals will sound good when played harmonically like the fifth. Other intervals will sound dissonant (Nashaz) like the tritone. You should also be able to differentiate between the minor third and the major third, because this is the only difference between major and minor chords, as we should see later. There are various books with cassette tapes for ear training (most notably those by David N. Baker). There are also various software tutorial programs