Understanding and applying the theory behind many of the jazz pieces you know and love and how they are played can be an enlightening area of study. It can greatly improve your approach to the pieces you play as you appreciate them from the inside out, and this knowledge will enrich your powers of improvisation. Jazz, just like any other genre of music, has its ideas based on theoretical concepts.
These concepts provide a framework for key musical elements such as harmony, structure, rhythm, and melody. It is vital to note however that in the same way the ‘rules’ of classical music are broken or modified by composers, so too are the rules and frameworks of jazz.
One of the key differences between jazz piano and say a jazz clarinet or trumpet is that the pianist can play more than just the melody. The jazz piano player must be confident enough to offer a harmony or chordal accompaniment to the melody not just play the melody alone. This means it is perhaps even more important that the jazz pianist has full and extensive knowledge of the workings of jazz harmony. Without this, the likely outcome will be weak. How those chords and the melody are practically handled by the jazz pianist is another matter that is about chord ‘voicing’. This, in a nutshell, means how the notes of any given chord are played by the pianist’s left hand.
What often singles out jazz from other genres of music is not only its characteristic ‘swing’ rhythm but also it’s use of harmony and scales. The jazz pianist needs to be acutely aware of the use of ‘extended chords including the 7th, 9th, 11th, and 13th. There are also diminished, half-diminished and augmented chords that feature in jazz, essential for creating the diversity of harmonic colour heard in many jazz tunes.
If we are considering the ides of the extended chord, then we need to remember that for jazz purposes the chords can be assembled across a range of two octaves. Once you reach the first octave, say from C to C, then the next note of the C major scale is D. This is counted as the 9th, the F, the 11th, and the A, the 13th. These notes are frequently part of the jazz chord progressions giving each tune a unique flavour.
Sometimes these more elaborate chords are used to ‘blur’ the harmony and allow for more free improvisational possibilities. A competent jazz pianist knows just how to play the underlying chords during a solo to not only provide the harmonic support but also to present open melodic options. Instead of simply playing a G7 chord with G in the root, you could extend the chord to include an A-flat (flattened 9th), and an E (13th) and play the chord from the F upwards giving an F – Ab – B – E chord.
At first glance, this may not look like a G7 chord but this is precisely the kind of technique employed by jazz artists to give a distinct sound to their interpretation of the music. It also means that the solo line over the top of the chord has more freedom to move in directions that are not so firmly connected to the chord of G7.
Along with chords come certain cornerstone chordal progressions that every jazz musician needs to know by ear and by eye. The ‘turnaround’ is one of the most common, so-called because it often comes at the end of a section or musical phrase. If the piece was in the key of D major for instance, then the turnaround would be Em – A(7) or ii – V7. This harmonically leads back to the ‘tonic’ chord or home key of the piece.
To bring a touch of jazz colour to this popular harmonic feature is to ‘substitute’ the 5th chord (V7) for one a tri-tone above. If A(7) is the 5th chord then this would mean substituting it for an Eb(7) chord, keeping in mind that a tri-tone means exactly three tones away from the starting note. This gives a new turnaround of Em (ii), Eb(7) leading to D. Notice how the result of this progression is a ‘chromatic’ descent from E to D. Harmonically it is convincing because of this.
All of the above makes even more sense when you have a firm grasp of the musical keys. By this, I refer to all the major and minor keys common to the Western Tonal system. One suggested an approach to learning these that I have used with students is through the ‘circle of 5ths’. The reason this works is it is an easy way of playing through all of the keys in a single go.
Here is how it works. If you are looking at the ‘major’ keys then follow this order of notes or chords: C – G – A – D – E – B – F# – Db – Ab – Eb – Bb – F – C. Each note follows the interval or gap between the notes of a 5th and progresses through each major key in turn. If you want to play through the minor keys then it is the ‘circle of 4ths’ that is less well-known but equally useful. (Am – Dm – Gm – Cm – Fm – Bbm – Ebm – Abm(G#) – C#m – F#m – Bm – Em – Am). Not only does this process take you through all the keys but it shows you how you can move or modulate smoothly from one key to the next until you end up where you began.
Alongside the keys, chords and progressions being fluent with a variety of scales is a basic requirement for the jazz pianist. Learning each of the major and minor scales is vital and being able to ‘swing’ them. There is also the ‘blues scale with flattened 3rd, 5th, and 7th notes, the ‘pentatonic’ that for the major version would be the notes 1,2, 3, 5 and 6 of the major scale. This one is useful in many solos as it ‘avoids’ those notes that can sound like you have made a mistake. In addition to the scales being able to play the arpeggios (notes 1, 3 and 5 of any scale), plus their extensions, 7ths especially is a distinct advantage to the jazz pianist.
This by no means covers everything you need to know but does introduce some central concepts that are involved in being a jazz piano player. What is essential is to become familiar with the Jazz Standards and the work of professional jazz pianists.