Seventh chords are four-note chords composed of a triad with an added seventh interval above its root. Although triads may be perceived as consonant, seventh chords require careful voice-leading in order to sound musically satisfactory.
Understanding and using seventh chords will expand your harmonic vocabulary, giving you access to creating different moods and textures on the piano. There are five categories of seventh chords which can be categorize by interval quality:
Major Seventh
Major seventh chords are popularly employed in classical and romantic pieces alike, and are considered more romantic and tranquil compared to the dissonant dominant seventh chord. Plus, they’re easy to play! Simply combine a major triad with a major seventh and lower it by one half step in order to form the major diminished 7th chord.
When building these chords, it is essential to remember that the 7th note does not belong to the root chord itself but acts as a separate note above it, creating tension between its three notes and their sevenths.
To identify the quality of a seventh chord, it’s essential to have knowledge of how to read notes on a piano keyboard. The first step should be referencing a complete scale note interval table and noting the amount of half-tones/semisonnes between root note and 3rd, 5th and 7th notes (note that 1st column/scale degree corresponds with middle C) on scale note interval table – these numbers will identify each triad quality name.
Minor Seventh
Seventh chords are composed of triads with an additional pitch sounding a seventh above their root note. By adding this dissonant interval, seventh chords create richer harmonic textures than their traditional triad counterparts and can be found across a variety of musical genres such as jazz, R&B and Blues.
Minor seventh chords can be created in two ways, either by stacking thirds or altering the notes of a major seventh chord. Here we’ll use an A minor triad with its root, lower 3rd, and 5th notes lowered one half step each for our minor seventh chord creation.
Music notation often indicates the seventh of a seventh chord by using a slash followed by the letter representing its root in the bass voice, commonly referred to as a “figured bass.” This notation is usually employed when dealing with chords featuring sevenths which occur within their bass voice – such as this A minor seventh chord.
Dominant Seventh
The dominant seventh, more commonly referred to as V7 or dom 7, is one of the most frequently-encountered seventh chords, typically comprised of a major triad and an interval of 10 semitones above its root note.
A dominant seventh chord may be left unchanged or altered according to its function in a song and the accompaniment by comping instruments. Unaltered dominant sevenths are usually indicated with a 7 (although they may also be written as 5, 13, etc).
A chord that contains a b13 is an altered dominant seventh chord and usually indicated with 13 in music notation. Both forms of dominant seventh are utilized, though the former often sounds more bluesy than its counterpart, 5. Additionally, chords containing b13 may also be played in second or third inversion to create different sounds; this feature can especially benefit pianists with smaller hands since this allows them to ‘cheat’ on thirds that would otherwise be hard to reach when in solid form.
Half-Diminished Seventh
The half-diminished seventh chord is one of the more dissonant types of 7th chords, adding tension or sadness to your piece. Unlike tritone chords which contain perfect 5th intervals, this chord does not contain one and thus sounds less stable than others.
Therefore, this chord can be more unstable than other seventh chords and is generally used as a link between other chords rather than being played as its tonic chord. Yet its beauty remains evident even with its instability.
Schoenberg’s Song of the Wood Dove contains an outstanding example of his use of chromaticism in his works, as evidenced by this excerpt. For instance, Jacobsen’s text does not align it with its tonic chord; instead it introduces a functionally mixed sonority which eventually resolves in measure 1107 with a dominant seventh F triad chord in measure 1107.