# Intervals In Music Definition Essay

## Music Intervals

*I am currently converting the entire Essential Music Theory site to https to give visitors a more secure browsing experience. Everything should be fine but apologies if anything doesn't work quite as expected over the next couple of weeks. *

*Simon (12 November 2017)*

**Working out music intervals is easy** once you know how, and this page tells you how! The key to working out intervals is to learn about them step-by-step. Having some knowledge of scales is essential and if you don't already know how to work out a major scale you need to learn. *I am working on a page about scales at the moment so there will be a link here soon!*

At the simplest level

**an interval is the distance between two notes**.

So to begin with, all you need to do is count!

How to calculate an interval

To find the interval between 2 notes just find the pitch of the *lowest* note and start counting until you reach the top note. When counting intervals you always **start from the bottom note** and **count both notes**. E.g., to find the interval between C and G, begin on C and count up the scale until you reach G.

E.g. **C**(1) **D**(2) **E**(3) **F**(4) **G**(5)

So *t**he interval between C and G is a fifth.*

See how easy the first step is? Here is another example

In the example above we count

**D**(1) **E**(2) **F**(3) **G**(4) **A**(5) **B**(6)

So the interval from D to B is a sixth.

If the interval is an **8th** it can be written as an **octave**. If an interval notes are at the **same pitch** it is called a **unison** To start with all intervals will be an octave or less. Compound intervals (bigger than an octave) come later!

This first step doesn't take any sharps or flats in the scale into account, it merely calculates the distance between the notes, but as one of my piano students often remarks “baby steps”. When studying music theory this is particularly true. Having a clear understanding of the basics is crucial when things become more complicated later on. In fact, a clear understanding of basics means that the “complicated parts” are easy as well! Note the words “clear understanding," for me this is very different from a “good knowledge”. In music theory a “good knowledge” is not as important as a “clear understanding”

Take this Simple Intervals Quiz to check your understanding of music theory intervals.

## The quality of music intervals

In addition to a number (distance) intervals also have a *quality*. This distinguishes intervals which are not part of the major scale. The 5 qualities of intervals are **major, minor, perfect, augmented and diminished**. Double augmented and double diminished intervals are not common. To begin with we will look at 3 of these qualities. Major, Minor and Perfect Intervals.

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Return to the **Essential Music Theory Homepage** from Music Intervals

For albums named Intervals, see Interval (disambiguation).

In music theory, an **interval** is the difference between two pitches.^{[1]} An interval may be described as **horizontal**, **linear**, or **melodic** if it refers to successively sounding tones, such as two adjacent pitches in a melody, and **vertical** or **harmonic** if it pertains to simultaneously sounding tones, such as in a chord.^{[2]}^{[3]}

In Western music, intervals are most commonly differences between notes of a diatonic scale. The smallest of these intervals is a semitone. Intervals smaller than a semitone are called microtones. They can be formed using the notes of various kinds of non-diatonic scales. Some of the very smallest ones are called commas, and describe small discrepancies, observed in some tuning systems, between enharmonically equivalent notes such as C♯ and D♭. Intervals can be arbitrarily small, and even imperceptible to the human ear.

In physical terms, an interval is the ratio between two sonic frequencies. For example, any two notes an octave apart have a frequency ratio of 2:1. This means that successive increments of pitch by the same interval result in an exponential increase of frequency, even though the human ear perceives this as a linear increase in pitch. For this reason, intervals are often measured in cents, a unit derived from the logarithm of the frequency ratio.

In Western music theory, the most common naming scheme for intervals describes two properties of the interval: the quality (perfect, major, minor, augmented, diminished) and number (unison, second, third, etc.). Examples include the minor third or perfect fifth. These names identify not only the difference in semitones between the upper and lower notes, but also how the interval is spelled. The importance of spelling stems from the historical practice of differentiating the frequency ratios of enharmonic intervals such as G–G♯ and G–A♭.^{[4]}

## Size[edit]

The size of an interval (also known as its width or height) can be represented using two alternative and equivalently valid methods, each appropriate to a different context: frequency ratios or cents.

### Frequency ratios[edit]

Main article: Interval ratio

The size of an interval between two notes may be measured by the ratio of their frequencies. When a musical instrument is tuned using a just intonation tuning system, the size of the main intervals can be expressed by small-integer ratios, such as 1:1 (unison), 2:1 (octave), 3:2 (perfect fifth), 4:3 (perfect fourth), 5:4 (major third), 6:5 (minor third). Intervals with small-integer ratios are often called *just intervals*, or *pure intervals*.

Most commonly, however, musical instruments are nowadays tuned using a different tuning system, called 12-tone equal temperament. As a consequence, the size of most equal-tempered intervals cannot be expressed by small-integer ratios, although it is very close to the size of the corresponding just intervals. For instance, an equal-tempered fifth has a frequency ratio of 2^{7⁄12}:1, approximately equal to 1.498:1, or 2.997:2 (very close to 3:2). For a comparison between the size of intervals in different tuning systems, see section Size in different tuning systems.

### Cents[edit]

Main article: Cent (music)

The standard system for comparing interval sizes is with cents. The cent is a logarithmic unit of measurement. If frequency is expressed in a logarithmic scale, and along that scale the distance between a given frequency and its double (also called octave) is divided into 1200 equal parts, each of these parts is one cent. In twelve-tone equal temperament (12-TET), a tuning system in which all semitones have the same size, the size of one semitone is exactly 100 cents. Hence, in 12-TET the cent can be also defined as one hundredth of a semitone.

Mathematically, the size in cents of the interval from frequency *f*_{1} to frequency *f*_{2} is

## Main intervals[edit]

The table shows the most widely used conventional names for the intervals between the notes of a chromatic scale. A perfect unison (also known as perfect prime)^{[5]} is an interval formed by two identical notes. Its size is zero cents. A semitone is any interval between two adjacent notes in a chromatic scale, a whole tone is an interval spanning two semitones (for example, a major second), and a tritone is an interval spanning three tones, or six semitones (for example, an augmented fourth).^{[a]} Rarely, the term ditone is also used to indicate an interval spanning two whole tones (for example, a major third), or more strictly as a synonym of major third.

Intervals with different names may span the same number of semitones, and may even have the same width. For instance, the interval from D to F♯ is a major third, while that from D to G♭ is a diminished fourth. However, they both span 4 semitones. If the instrument is tuned so that the 12 notes of the chromatic scale are equally spaced (as in equal temperament), these intervals also have the same width. Namely, all semitones have a width of 100 cents, and all intervals spanning 4 semitones are 400 cents wide.

The names listed here cannot be determined by counting semitones alone. The rules to determine them are explained below. Other names, determined with different naming conventions, are listed in a separate section. Intervals smaller than one semitone (commas or microtones) and larger than one octave (compound intervals) are introduced below.

## Interval number and quality[edit]

In Western music theory, an interval is named according to its *number* (also called *diatonic number*) and *quality*. For instance, *major third* (or **M3**) is an interval name, in which the term *major* (**M**) describes the quality of the interval, and *third* (**3**) indicates its number.

### Number[edit]

The number of an interval is the number of letter names it encompasses or staff positions it encompasses. Both lines and spaces (see figure) are counted, including the positions of both notes forming the interval. For instance, the interval C–G is a fifth (denoted **P5**) because the notes from C to the G above it encompass five letter names (C, D, E, F, G) and occupy five consecutive staff positions, including the positions of C and G. The table and the figure above show intervals with numbers ranging from 1 (e.g., **P1**) to 8 (e.g., **P8**). Intervals with larger numbers are called compound intervals.

There is a one-to-one correspondence between staff positions and diatonic-scale degrees (the notes of a diatonic scale)^{[d]}. This means that interval numbers can be also determined by counting diatonic scale degrees, rather than staff positions, provided that the two notes that form the interval are drawn from a diatonic scale. Namely, C–G is a fifth because in any diatonic scale that contains C and G, the sequence from C to G includes five notes. For instance, in the A♭-major diatonic scale, the five notes are C–D♭–E♭–F–G (see figure). This is not true for all kinds of scales. For instance, in a chromatic scale, the notes from C to G are eight (C–C♯–D–D♯–E–F–F♯–G). This is the reason interval numbers are also called *diatonic numbers*, and this convention is called *diatonic numbering*.

If one adds any accidentals to the notes that form an interval, by definition the notes do not change their staff positions. As a consequence, any interval has the same interval number as the corresponding natural interval, formed by the same notes without accidentals. For instance, the intervals C–G♯ (spanning 8 semitones) and C♯–G (spanning 6 semitones) are fifths, like the corresponding natural interval C–G (7 semitones).

Notice that interval numbers represent an inclusive count of encompassed staff positions or note names, not the difference between the endpoints. In other words, one starts counting the lower pitch as one, not zero. For that reason, the interval C–C, a perfect unison, is called a prime (meaning "1"), even though there is no difference between the endpoints. Continuing, the interval C–D is a second, but D is only one staff position, or diatonic-scale degree, above C. Similarly, C–E is a third, but E is only two staff positions above C, and so on. As a consequence, joining two intervals always yields an interval number one less than their sum. For instance, the intervals C–E and E–G are thirds, but joined together they form a fifth (C–G), not a sixth. Similarly, a stack of three thirds, such as C–E, E–G, and G–B, is a seventh (C–B), not a ninth.

This scheme applies to intervals up to an octave (12 semitones). For larger intervals, see § Compound intervals below.

### Quality[edit]

The name of any interval is further qualified using the terms **perfect** (**P**), major (**M**), minor (**m**), augmented (**A**), and diminished (**d**). This is called its *interval quality*. It is possible to have doubly diminished and doubly augmented intervals, but these are quite rare, as they occur only in chromatic contexts. The quality of a compound interval is the quality of the simple interval on which it is based.

#### Perfect[edit]

Perfect intervals are so-called because they were traditionally considered perfectly consonant^{[6]}, although in Western classical music the perfect fourth was sometimes regarded as a less than perfect consonance, when its function was contrapuntal.^{[vague]} Conversely, minor, major, augmented or diminished intervals are typically considered less consonant, and were traditionally classified as mediocre consonances, imperfect consonances, or dissonances.^{[6]}

Within a diatonic scale^{[d]} all unisons (**P1**) and octaves (**P8**) are perfect. Most fourths and fifths are also perfect (**P4** and **P5**), with five and seven semitones respectively. One occurrence of a fourth is augmented (**A4**) and one fifth is diminished (**d5**), both spanning six semitones. For instance, in a C-major scale, the **A4** is between F and B, and the **d5** is between B and F (see table).

By definition, the inversion of a perfect interval is also perfect. Since the inversion does not change the pitch class of the two notes, it hardly affects their level of consonance (matching of their harmonics). Conversely, other kinds of intervals have the opposite quality with respect to their inversion. The inversion of a major interval is a minor interval, the inversion of an augmented interval is a diminished interval.

#### Major and minor[edit]

As shown in the table, a diatonic scale^{[d]} defines seven intervals for each interval number, each starting from a different note (seven unisons, seven seconds, etc.). The intervals formed by the notes of a diatonic scale are called diatonic. Except for unisons and octaves, the diatonic intervals with a given interval number always occur in two sizes, which differ by one semitone. For example, six of the fifths span seven semitones. The other one spans six semitones. Four of the thirds span three semitones, the others four. If one of the two versions is a perfect interval, the other is called either diminished (i.e. narrowed by one semitone) or augmented (i.e. widened by one semitone). Otherwise, the larger version is called major, the smaller one minor. For instance, since a 7-semitone fifth is a perfect interval (**P5**), the 6-semitone fifth is called "diminished fifth" (**d5**). Conversely, since neither kind of third is perfect, the larger one is called "major third" (**M3**), the smaller one "minor third" (**m3**).

Within a diatonic scale,^{[d]} unisons and octaves are always qualified as perfect, fourths as either perfect or augmented, fifths as perfect or diminished, and all the other intervals (seconds, thirds, sixths, sevenths) as major or minor.

#### Augmented and diminished[edit]

Augmented intervals are wider by one semitone than perfect or major intervals, while having the same interval number (i.e., encompassing the same number of staff positions). Diminished intervals, on the other hand, are narrower by one semitone than perfect or minor intervals of the same interval number. For instance, an augmented third such as C–E♯ spans five semitones, exceeding a major third (C–E) by one semitone, while a diminished third such as C♯–E♭ spans two semitones, falling short of a minor third (C–E♭) by one semitone.

The augmented fourth (**A4**) and the diminished fifth (**d5**) are the only augmented and diminished intervals that appear in diatonic scales^{[d]} (see table).

### Example[edit]

Neither the number, nor the quality of an interval can be determined by counting semitones alone. As explained above, the number of staff positions must be taken into account as well.

For example, as shown in the table below, there are four semitones between A♭ and B♯, between A and C♯, between A and D♭, and between A♯ and E, but

- A♭–B♯ is a second, as it encompasses two staff positions (A, B), and it is doubly augmented, as it exceeds a major second (such as A–B) by two semitones.
- A–C♯ is a third, as it encompasses three staff positions (A, B, C), and it is major, as it spans 4 semitones.
- A–D♭ is a fourth, as it encompasses four staff positions (A, B, C, D), and it is diminished, as it falls short of a perfect fourth (such as A–D) by one semitone.
- A♯-E is a fifth, as it encompasses five staff positions (A, B, C, D, E), and it is triply diminished, as it falls short of a perfect fifth (such as A–E) by three semitones.

## Shorthand notation[edit]

Intervals are often abbreviated with a **P** for perfect, **m** for minor, **M** for major, **d** for diminished, **A** for augmented, followed by the interval number. The indication M and P are often omitted. The octave is P8, and a unison is usually referred to simply as "a unison" but can be labeled P1. The tritone, an augmented fourth or diminished fifth is often **TT**. The interval qualities may be also abbreviated with **perf**, **min**, **maj**, **dim**, **aug**. Examples:

- m2 (or min2): minor second,
- M3 (or maj3): major third,
- A4 (or aug4): augmented fourth,
- d5 (or dim5): diminished fifth,
- P5 (or perf5): perfect fifth.

## Inversion[edit]

Main article: Inversion (music)

A simple interval (i.e., an interval smaller than or equal to an octave) may be inverted by raising the lower pitch an octave or lowering the upper pitch an octave. For example, the fourth from a lower C to a higher F may be inverted to make a fifth, from a lower F to a higher C.

There are two rules to determine the number and quality of the inversion of any simple interval:^{[7]}

- The interval number and the number of its inversion always add up to nine (4 + 5 = 9, in the example just given).
- The inversion of a major interval is a minor interval, and vice versa; the inversion of a perfect interval is also perfect; the inversion of an augmented interval is a diminished interval, and vice versa; the inversion of a doubly augmented interval is a doubly diminished interval, and vice versa.

For example, the interval from C to the E♭ above it is a minor third. By the two rules just given, the interval from E♭ to the C above it must be a major sixth.

Since compound intervals are larger than an octave, "the inversion of any compound interval is always the same as the inversion of the simple interval from which it is compounded."^{[8]}

For intervals identified by their ratio, the inversion is determined by reversing the ratio and multiplying by 2. For example, the inversion of a 5:4 ratio is an 8:5 ratio.

For intervals identified by an integer number of semitones, the inversion is obtained by subtracting that number from 12.

Since an interval class is the lower number selected among the interval integer and its inversion, interval classes cannot be inverted.

## Classification[edit]

Intervals can be described, classified, or compared with each other according to various criteria.

Interval inversions

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