Seventh chords are key components to expanding your harmonic repertoire on the piano, as they create atmosphere and texture across virtually all genres of music.
A seventh chord can be thought of as a triad with an extra interval added, with its quality determining its qualities as a seventh chord. Common seventh chords include major and minor varieties.
Major Seventh
The major seventh chord is an extremely common and versatile part of tonal music, serving many purposes. Constructed from a major triad and the addition of one half step below its root note (thus creating a dissonant interval that must be resolved), it serves a variety of functions.
Root notes of seventh chords stacked closely are known as roots; all other notes are named according to their generic intervals above it; for instance an A minor seventh chord contains the notes C-Eb-Gb-Bbb as its notes.
To create a major seventh chord, begin by drawing its root note onto the staff. Next, apply any accidentals from its key signature to its root note of the triad’s root note. Finally, draw an extra-long snowperson representing its major seventh interval above its origin (Fig. 18-6).
Minor Seventh
Seventh chords have long been used as part of modern and classical music composition, dating all the way back to Claude Debussy’s romantic classic “Claire de Lune.” They add depth, emotion, and complexity to triads and are commonly employed across modern genres like pop, jazz, R&B blues and film music.
Contrary to consonant triads, seventh chords contain an additional pitch which makes them inherently dissonant and must be handled carefully in order to minimize dissonance. Luckily, there are various strategies and solutions for managing seventh chords so as to minimize dissonance and prepare them appropriately for performance.
One of the most frequently employed techniques is falling-fifth root motion, in which seventh chord’s seventh note is resolved down by one fifth to form next chord (see Example 18-10 for clarity). This example shows this method at work.
To form a minor seventh chord, simply combine a minor triad (root to three) with a major third (3-5) using open spacing. However, note that any doubled notes must be flattened through enharmonic equivalence to avoid fret buzz caused by overreaching your fingers too high and reaching too far up the fretboard.
Half-Diminished Seventh
Over centuries, musicians and theorists alike have found it challenging to grasp the enigma of the diminished seventh chord. Its complexity lies partly in its multiple functions; audibly too, its root may be difficult to pinpoint given that there is no definitive tertian base.
Solution to this problem lies within intervals. Any chord can be formed over any note by stacking minor thirds and major thirds according to an interval pattern; for instance, in C major, the Bmb5 chord (or B-chord) can be seen as a diatonic seventh chord as its notes create a minor third that stacks atop two major ones – similar to how any chord can be constructed above any note by using an interval pattern like Bmb5.
To create a diminished seventh chord above any note, one must add a fifth to this pattern and create an extended diminished triad with a diminished seventh (sometimes known as flat seven chord). Standard music notation uses an open circle with 7 as notation for this chord type.
Fully Diminished Seventh
A fully diminished seventh chord is formed from a minor triad with an added diminished fifth, creating a tritone (three half steps between third and seventh notes of chord), making it feel tense and dissonant. It is often used as the second chord in an ii-V7-i progression.
To create a fully diminished seventh chord, start from the root of a triad and add accidentals from its key signature to each of its third, fifth, and seventh notes; for instance a Cmi7 chord would include an F# in its bass note.
Another effective method for creating fully diminished seventh chords is through drop 2-voicing. This technique involves moving the second highest note down into the bass note of the chord voicing; this effectively creates four chords within one, and works especially well when dealing with diminished chords.