Seventh chords are four-note chords whose notes can be stacked in thirds. As with triads, seventh chords can also be classified according to their qualities of being major, minor, dominant or half-diminished.
A major seventh chord can be created by taking a major triad and adding a major seventh above its root note, creating an arrangement consisting of C, E, G and B notes.
Major Seventh
Each seventh chord has a name that describes its quality. To do this, draw the root note onto a staff and add notes a third, fifth and seventh above it (imagine drawing an extended snowperson). The distance between these three chords and the root note will reveal its quality as a seventh chord.
The major seventh chord is one of the most iconic chords in music, often used to add tension and power. It stands out due to its distinctive sound created by its interval of one major seventh from its root note.
This chord is formed by taking a major triad and flattening its fifth, creating a diminished seventh (9 semitones above the root). This chord can often be heard in jazz standards that utilize ii-V-i progressions in minor keys; its intense yet dissonant sound often makes recordings difficult to hear clearly, yet jazz musicians continue to use this chord frequently.
Minor Seventh
This chord is often employed in jazz and blues music to create tension before tonic chords are played.
Minor seventh chords consist of a minor triad and one or both minor seventh intervals – major seventh or minor seventh – added above the root note to form a seventh chord.
The minor seventh chord is similar to its dominant seventh counterpart but less complex and features an ‘jazzy’ sound, making it particularly suitable for blues and rock music.
Chords can be classified according to four qualities (Major, Dominant, Minor and Half-Diminished). Each chord consists of a triad with one extra note added – usually either Major or Minor third above its fifth string – which forms its base chord. Since all triads and seventh chords follow a cycle of thirds we can easily identify each by its letter name from this set of threes.
Dominant Seventh
The dominant seventh chord is a highly versatile chord used in various genres of music. It often produces tension and instability before finally being resolved to its tonic chord (I) to establish key change.
To construct a dominant seventh chord, start by beginning with the root of a major triad and adding a flatted seventh to it. If the roots of this major triad lie within a minor key signature, add any necessary accidentals from that signature in order to achieve the appropriate sound.
7th chords have a variety of qualities, including diminished, half-diminished, minor, major-minor, augmented and augmented-major chords. Each chord quality includes an interval table showing its first, third and fifth notes from scales in that key, with names adjusted according to half notes / semitones / piano keys depending on its quality.
Names for dominant seventh chords contain their chord qualities in their symbol to facilitate easy reading; for instance, G7 would include G, B, D and F# in its name.
Half-Diminished Seventh
The half-minished seventh chord is an integral component of jazz harmonic language. With its dissonant sound, this chord adds tension to any progression and can even be used to emphasize certain notes or melodic lines.
Diminished sevenths are similar to major sevenths, except their third is lowered by half step to form diminished sevenths. This creates a dissonant sound that’s more tense and discordant than major sevenths but not as sharp as minor sevenths; these notes can often be used to create tension and unease.
Find this chord on any minor scale’s diatonic II chord; it often acts as the dominant and leads smoothly into its V chord climax. Furthermore, it works well in other tonal contexts and is typically written with a circle and slash through it; for instance Cm7(b5); it may also be known by some as Ebm7(b5).