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What Is an Interval in Music? A Comprehensive Guide

August 4, 2023
what is an interval in music

Those gaps between notes are easy to miss as a newcomer to music theory, and most of us pay them no mind as casual listeners.

But dig a little deeper, and you’ll find that they are absolutely vital.

Intervals tell us, as musicians, the distance between any given note. 

On a technical level, the foundations of music, like scales and chords, would not be possible at all without intervals.

Intrigued?

Want to know more?

Let’s get to know intervals more intimately and answer the question, ‘what is an interval in music?’.

What is an Interval? 

An interval in music is a distance in pitch between any two musical notes.

Any time you have more than one note, there’s an interval between those notes.

The larger the interval between any two notes, the greater the difference in pitch quality between those notes.

Notes with only a few intervals between them sound more similar in pitch.

For instance, two neighboring keys on the piano have a similar pitch.

We can describe intervals in three ways: the distance of the interval, the quality of the interval, and whether it is harmonic or melodic.

There are both simple intervals, up to one octave, and compound intervals.

Tones and Semitones

The smallest types of intervals are represented by semitones and tones, also known as half-steps and steps.

They are the foundation of all intervals between notes.

We use combinations of semitones and tones to build the scales that underlie all music.

As a refresher, the semitone is the smallest interval on the piano.

It can be visualized by thinking of the interval between one key.

A whole tone is the second smallest interval between two keys.

interval between 2 keys

Numbered Intervals

number intervals

Larger intervals are described using numbers (also called diatonic numbers) depending on how many letter names of the musical “alphabet” are between the two given notes. 

The notes C and D are two letters apart on piano, for instance, and are referred to as an interval of a 2nd.

The notes C and E are three letters apart, so what would you venture this interval is called?

Round of applause: This interval is a 3rd. Not so complicated, right?

  • C and F are four letters apart, so this interval is a 4th. 
3rd interval
  • C and G are five letters apart, so this interval is a 5th.
  • C and A are six letters apart, so this interval is a 6th.
5th and 6th interval
  • C and B are seven letters apart, so this interval is a 7th.
  • C and the C above it on the piano are 8 letters apart but are typically not called an 8th. You will recognize their common name: an octave. The interval octave is eight notes higher than the base note, otherwise called the tonic.

When one of the notes has a pitch that is exactly double the pitch of the other note, that, my dear, is an octave.

These are the main intervals from C:

main intervals from C

Unison Intervals

Unison intervals are intervals between the same note.

Wait, what?

Relax.

A unison interval occurs when two instruments in an orchestra or arrangement play the same note at the same time.

When musicians write a harmonic unison interval, they write the notes next to each other.

Interval Quality

Before you relax too much, you need to know a few more features of intervals.

Intervals are described by the number between notes, but they are also described by their quality.

There are five different types of interval quality.

Perfect Intervals

In order to be a perfect interval, the upper note has to be in the major scale of the lower note.

The following are considered perfect intervals:

  • Perfect 4th
  • Perfect 5th
  • Perfect 8ve (or octave)

If the interval is a 4th, 5th, or an octave, but it is not in the major scale, then, sorry to disappoint, but it is not a perfect interval. 

Intervals such as the unison, fourth, fifth, and octave can be classified as “perfect,” but they are never classified as “major” or “minor” intervals. 

That being said, the second, third, sixth, and seventh intervals can be classified as major or minor but can never be classified as perfect.

Major Intervals

If the upper note of an interval is in the major scale of the lower note (and it’s not a 4th, 5th, or octave), then it is a major interval.

There are four intervals that are called major intervals:

  • Major 2nd
  • Major 3rd
  • Major 6th
  • Major 7th

When the lower note is the tonic and the upper note is in the major scale, it will be either perfect or major.

Reduced choices are always good when it comes to learning the basics, no? 

Minor Intervals

Take any of the major intervals and make them smaller by one semitone/half-step, and now you’ve got yourself a minor interval. 

If we took a C to an E, a major 3rd interval, and flattened it so that the E becomes a minor key, it will now be an example of a minor interval.

Kind of intuitive, right?

There are only four possible minor intervals, so put the flashcards away:

  • Minor 2nds
  • Minor 3rds
  • Minor 6ths
  • Minor 7ths

Keep in mind that all the notes above the tonic in a major scale are perfect or major.

How can we suss out whether an interval is minor?

Determine if the upper note is in the major scale.

If not, ask yourself whether the interval is a half step smaller than a major interval.

If yes, then you’ve got yourself a minor interval.

minor interval

Augmented Intervals

We call an interval an augmented interval when we extend a major or perfect interval by one semitone/half-step without changing its letter name.

You could consider this a bit of wizardry.

If we took a major second like F to G and made the G a G#, we have turned it into an augmented 2nd and made the interval wider by one semitone.

Keep in mind that every note in a major scale is either a major interval or a perfect interval when starting from the tonic note or the first note of the scale. 

Diminished Intervals

When we flatten a perfect interval by one semitone, we have a new quality entirely: a diminished interval

If we flatten the three perfect intervals, 4ths, 5ths, or octaves by one semitone, they become diminished rather than minor.

Keep in mind that there are no minor versions of perfect intervals, and they will always become diminished instead.

We can flatten minor intervals by a semitone, and then they become diminished.

If we flatten a major interval by a tone/whole step, then it, too, becomes a diminished interval.

Intervals of any size can be augmented or diminished.

Below is an augmented and diminished interval on C.

diminished interval on C

Here is a helpful visual for the major and minor intervals:

major and minor intervals

Here is a helpful visual for the perfect intervals:

perfect interval

Compound Intervals

Compound intervals are larger than one octave.

There are two different names for compound intervals.

The major 3rd interval, C – E, transforms into what we call a compound major 3rd when it is over an octave higher.

This is one way of naming compound intervals.

The second way of naming intervals is by introducing larger numbers into the game.

You can name the intervals the 9th, 10th, 11th, etc.  

Harmonic and Melodic Intervals

When we have two notes that are played at the same time by different instruments, we call them harmonic intervals.

Harmonic intervals are found in chords.

These are also referred to as vertical intervals.

A melodic interval is the opposite, which happens when two notes are played one after the next.

Melodic intervals are found in a sequence of notes, played note-by-note, as a melody.

These are also referred to as horizontal or linear intervals.

Interval Training

Skip the gym and do some musical interval training instead.

All it takes is dedication and focus, and the intervals will become second nature.

Understanding intervals (and their numbers and qualities) is fundamental to building chords, scales, and memorable music.

Happy studying.

You may also like: What Is a Key in Music?

Will Fenton

Will, the founder of MIDDER, is a multifaceted individual with a deep passion for music and personal finance. As a self-proclaimed music and personal finance geek, he has a keen eye for futuristic technologies, especially those that empower creators and the public.

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