A seventh chord consists of three notes combined into an interval that forms an interval of seven notes above its root chord, often resolved down one step to create its final form.
Sevenths add tension and resolution to chord progressions. There are five primary kinds of sevenths: Major, Minor, Dominant, Half-Diminished and Diminished.
Dominant
A dominant seventh chord consists of either a major or minor triad plus an added note that creates an interval of a flat seventh above its root chord – this tritone adds tension that gives dominant chords their unique sound.
Chords containing dominant intervals often resolve to the tonic triad in any key, because its tone corresponds with that of the dominant chord’s flat seventh tone.
As well as being used for cadential dominant chord progressions, tension-building intervals can also add tension and excitement to melodies – as shown by Hendrix’s song, “Then You Begin To Make It Better”, for an excellent example of this effect.
Major
C major is an “all-or-nothing” key, featuring no flats or sharps (Example 12). It has a natural seventh scale degree to give it gravitas back towards its tonic key.
Each major key has a relative minor counterpart in the minors; an easy way to find yours is starting on the first note of your major scale and counting back three half steps, or minor thirds, from there.
This key is often associated with heroic works such as Beethoven’s Emperor Symphony or La Traviata’s Chorale “Libiamo”. Additionally, it evokes feelings of joy and love while making brass instruments easier to play as well as romantic piano concertos more appealing to listeners. Furthermore, white represents this key in synesthesia.
Minor
Minor scales possess an emotive sound often associated with sadness. Additionally, they present us with numerous chord-building possibilities.
The natural minor scale, also referred to as Aeolian mode, is one of the most frequently used minor scales. This scale closely resembles major key signature with one exception – in harmonic minor scale this note has its seventh note sharpened for creating leading tone.
Harmonic minor scales can be easily created from any major key by counting down one and a half or three semitones from its tonic, while melodic minor scales have two lowered scale degrees that may make their calculation harder; nonetheless, learning these rules could prove invaluable when playing jazz guitar.
Half-Diminished
A half diminished chord, commonly known as a minor 7 flat 5 chord (m7b5) is composed of three minor triads with flattened fifths arranged so they form an open minor 7 flat 5. These chords can typically be found on diatonic II chords of the minor scale, and like their fully diminished counterpart they can serve as dominant chords.
Similar to its diminution counterpart, this chord offers great sounding versatility in your arsenal. What sets it apart from regular minor seven chords is its inclusion of a b5 note.
Clean Bandit’s hit song ‘Rather Be’ features this type of progression when transitioning from Gb diminished chord to F minor chord, creating an extremely dramatic yet melancholic feeling to the song. Additionally, using an m7b5 chord can build tension and anticipation within an audience.
Tritone
The tritone, also referred to as the Devil’s interval or diabolus in musica, is an extremely dissonant combination of two notes used often in rock and metal music to create an ominous or menacing sound – for instance Jimi Hendrix’s iconic track Purple Haze begins with an opening guitar riff featuring such a tritone between E and Bb that sounds especially unnerving and menacing.
Medieval and Renaissance composers were warned not to compose music with tritones because it could be challenging for singers. Once classical music rules were relaxed and composers began using chord progressions featuring tritones instead of dominant 7th chords as part of harmonic progressions that create tension and release in chords, composers quickly found new uses for them musically. Tritones can often provide tension while simultaneously offering resolution in harmony progressions.