In music theory, a seventh is a musical interval that spans seven diatonic scale degrees. It is an essential building block in many chords and harmonic progressions, and understanding its properties can greatly enhance your understanding of music theory.

The Basics: What is an Interval?

An interval is the distance between two notes in a musical scale. In Western music, we use a system of twelve pitches that repeat throughout octaves.

The distance between these pitches is called a half step or semitone. Two half steps make up a whole step or tone.

Diatonic Scales

Diatonic scales are the most common scales used in Western music. They consist of seven different pitches that follow a specific pattern of whole and half steps. The most common diatonic scales are the major and minor scales.

Seventh Intervals

A seventh interval is created by counting seven diatonic scale degrees from the starting note. For example, in the C major scale, if we start on the note C and count up seven scale degrees, we get to the note B. The distance between C and B is a seventh interval.

Types of Seventh Intervals

There are two types of seventh intervals: major sevenths and minor sevenths.

Major Seventh Intervals

A major seventh interval spans eleven semitones or half steps. It has a bright and slightly dissonant sound that creates tension in music. In jazz and popular music, it is often used to add color to chords.

Minor Seventh Intervals

A minor seventh interval spans ten semitones or half steps. It has a darker sound than the major seventh but still adds tension to chords. It is commonly found in blues and rock music.

Seventh Chords

Seventh intervals are an essential component of seventh chords. A seventh chord is a four-note chord that consists of a root, third, fifth, and seventh interval. There are four types of seventh chords: major seventh, dominant seventh, minor seventh, and half-diminished seventh.

Major Seventh Chords

A major seventh chord consists of a major triad (root, third, fifth) and a major seventh interval. It has a bright and jazzy sound that is often used in ballads and love songs.

Dominant Seventh Chords

A dominant seventh chord consists of a major triad and a minor seventh interval. It has a strong and tense sound that is commonly used in blues and rock music.

Minor Seventh Chords

A minor seventh chord consists of a minor triad (root, flat third, fifth) and a minor seventh interval. It has a melancholic sound that is often used in jazz ballads.

Half-Diminished Seventh Chords

A half-diminished seventh chord consists of a diminished triad (root, flat third, flat fifth) and a minor seventh interval. It has an unstable sound that creates tension in music.

In Conclusion

Understanding the properties of the seventh interval is crucial to understanding music theory. It is an essential element in many chords and harmonic progressions. By incorporating this knowledge into your music writing or performance, you can create more engaging and dynamic musical compositions.