Learning how to construct and identify seventh chords is central to jazz music theory – especially since these chords don’t appear on sheets of music!
In most western musical harmony situations, 7th chords shift towards becoming dominant 1 chords, so any scales you play over them must harmonise with their chord tones.
Major Seventh
The major seventh chord is an essential element of jazz harmony. Composed by combining the root, third, and seventh degrees of a major triad, its tonic octave G is often employed in jazz voicings with its root positioned at the bottom of chord.
Instead of thinking of sevenths as a separate form of harmony, it may be more useful to view them as extensions of triads. There are 15 combinations between any three chord and its seventh (M7, m7, dom7, dim7 and half dim7) that form sevenths.
Common-practice music typically only utilizes five of these possibilities; jazz employs all–and more! As audiences adapted to dissonant elements found within common-practice tonality, composers began exploring this area more freely.
Minor Seventh
Seventh chords play an integral part in jazz music, as with most forms. Their powerful gravitational pull on the tonic note can be exploited to add flavor via modulations or leading-tones (chord tones that sound a fifth above or below the root chord tone).
Minor seventh chords are one of the most prevalent seventh chords found in jazz, becoming increasingly prevalent as jazz evolved from early to classic (or common-practice) harmony. Unlike its major counterpart, minor sevens cannot easily be converted to dominant chords by moving their roots to fifth position – unlike its major cousin.
Minor seventh chords are constructed using stacking minor triads. There are two basic forms for minor seventh chords: m7b5 and m7#5. Each can be further customized by adding either flattened fifths (m7b5 or m7#5) or diminished seventh intervals (m7bd or m7#d). While not frequently found in jazz music, diminished seventh intervals do occasionally appear as substitutes for major sevenths in some tunes.
Half-Diminished Seventh
Half-minished seventh chords can be an excellent way to add secondary dominant functions in minor keys or lead into major dominants, and are an effective appoggiatura chord choice.
For optimal learning of chords, it is best to start slowly by mastering one set of strings before moving up the neck – this way you will become acquainted with them all over the fretboard.
Each chord has a note interval quality (diminished, minor, major, perfect or augmented) which determines if sharp or flat accidentals must be added to any notes in its chord structure. Below are these interval qualities with their short names or abbreviations.
A half diminished seventh chord is usually represented by the symbol m7b5. This minor seventh chord features a flattened fifth, such as Cmin7b5. Sometimes written with a circle with an slash through it to signify this type of chord, the symbol itself often looks similar.
Barre Seventh
As a jazz guitarist, you should be familiar with this chord family. Mastering its barre chord shapes may require physical strength and dexterity, which requires practice to master. Regular practice of these chords will develop your finger strength.
To create this chord shape, your second finger bars strings 4-2 while your first finger plays the fret 5 note on string 1. The key to successfully constructing this chord shape is getting the fourth string ringing clearly; you may require some experimentation in finding out the optimal amount of pressure required to allow this.
This chord quality can be used to build more advanced jazz chords, such as minor 9ths and altered extension sevenths. Additionally, it serves as an anchor chord when soloing over it; Joe Pass often used this technique during his chord solos.