# Perfect fourth

In music theory, a perfect fourth is an interval that has five half steps (semitones). Explanations and excerpts from famous works

In music theory, a perfect fourth is an interval that has five half steps (semitones ).

The perfect fourth requires that:

• The interval must be a perfect fourth interval (four note names between the first and the last).
• The interval must have five half steps.

## What does a perfect fourth look like?

Here is an example of a melodic perfect fourth (two music notes in a melody) and a harmonic perfect fourth (in a chord):

## How to recognize a perfect fourth?

Rule of music theory: All intervals in a major scale starting with the tonic (degree I) are either major or perfect, and only unison, octave, fourth and fifth are perfect (the others are major).

Example with the interval A♭ / D♭:

Let's take the A flat major scale to have A♭ as the tonic:

From the rule stated above, it becomes clear that A♭ / D♭ is a perfect fourth.

## Inversion of the perfect fourth

The inversion of the perfect fourth is the perfect fifth.

Here is an example of a perfect fifth:

## Musical examples of perfect fourth

### Eine kleine Nachtmusik, Mozart

One of the famous examples of the use of perfect fourths can be found in Eine kleine Nachtmusik (a Little Night usic) by Mozart:

## Interval identification game

You will find this interval in my Intervals identification game:

Find all my music theory games by clicking this link music theory games

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