The dominant seventh chord is one of the most used in music and can help add tension and emotion.
As with triads, seventh chords consist of four notes connected by an unbroken chain and can be identified based on their quality. Roman numeral notation indicates this with a slash over the chord symbol (G7/F in Roman numeral notation).
Scales
Major seventh chords are an extension of the basic triad (1 3 5). Their sound can be highly dramatic, which is why Romantic-era piano pieces and many jazz standards incorporate them.
To create a major 7th chord, draw the root of a triad on the staff and add notes a third, fifth and seventh above it (imagine drawing an extended snowperson). Their names depend on their generic intervals – for instance C maj7 contains C E G notes.
Minor 7th chords can be more complex to play because they require flattening out the fifth of a root triad to form its diminished form, with notation being more complex (see table for an overview) as they employ notes outside their key signature, therefore needing accidentals for accompaniment.
Triads
If you have ever read any music theory book, chances are there is an introduction or section on triads in it. Triads are three-note chords made up of root, third and fifth notes; adding sevenths makes the chord an seventh chord.
Seventh chords are a type of triad which feature a seventh interval that may be major, minor, diminished or augmented above its root note. Their quality depends on which interval is used as well as which scale it’s built from.
A seventh chord can be identified by drawing its root on the staff and writing its notes plus either a major, minor, or diminished seventh above it (for instance 1-8). Most textbooks also utilize Roman numerals to identify triadic shapes and their inversions.
Major
Major seventh chords consist of a major triad with an extra major seventh placed above it, represented on the Circle of Fifths by a triangle.
There are five qualities of seventh chords. Three contain a perfect fifth between their root and third: minor seventh, major-minor seventh, and dominant seventh (V7). Two others are built around diminished triads: half-diminished seventh and fully diminished seventh.
To create a basic seventh chord, draw its root on the staff, add any accidentals from its key signature which apply to its notes, then below this root draw an extra-long snowperson representing notes a major third, minor fifth, and major seventh above it.
Minor
When a triad includes a minor seventh, it can be known as a minor 7th chord. If the 7th chord has both major third and minor seventh harmonics, it may also be classified as either major/minor or dominant (major/minor).
Named 7th chords can also be determined by their interval structure above their root note. The lowest note in any stacked triad known as its root and all notes above it as quality notes make up what we know as 7th chords.
Triad quality can be identified by adding an uppercase Roman numeral to its root note; VV7 indicates a major triad with a minor seventh between its root note and seventh note, while vivi7 denotes minor triads with such characteristics.
Diminished
Diminished seventh chords are essential components of modulation. Used primarily to connect key changes with new chords and act as connecting lines between different keys, diminished sevenths serve as the link.
They’re assembled using minor third intervals and built using either major or minor triads, starting with the lowest note as their root and ascending in minor thirds thereafter.
As chord structures become less consonant, their diminished form adds tension and longing for resolution – heightening its ultimate release all the more sweetly. They’re great choices for creating an atmosphere of vulnerability and wonder; use them to express sadness, surprise or any emotion calling for less consonant harmony.