Seventh Chords are essential in Jazz Performance.

An understanding of Seventh Chords is key to understanding Jazz Chords and Jazz Harmony. These chords are formed by taking the basic Triads ( Major, Minor, & Diminished ) and adding the note found at the 7th degree of the scale.

In the Key of C, using the scale notes [ C D E F G A B ]

C Major 7 is the composed of [ C E G B ]

Observe that the note [ B ], the 7th of the scale, is added to the basic C Major Triad [ C E G ] to arrive at the seventh chord C Major 7 Chord.

Taking this operation further, we can flat the 3rd degree, Note [ E ] to [ Eb ]. If we do that, we will also have to flat the 7th [ B ] to [ Bb ]. The energy attraction between the 3rd and 7th is so strong that if we avoid doing this, the chord doesn't sound right.

What we have then is seventh chord C Minor 7 [ C Eb G Bb ].

Going further, if we flat the 3rd, 5th, and 7th degrees, we get the C Half-diminished 7 or what is more commonly known as the C min7b5 chord [ C Eb Gb Bb ].

Finally, if we flat only the 7th degree [ B ] to [ Bb ], we get a new chord whose energy qualities lie somewhere between the Minor and Major and is considered Dominant because of its strong tendency to follow a Minor Chord and move toward a Major Chord. This pull is so elemental and so magnetic in its energy that it tends to dominate the progression.

This seventh chord is called C Dominant 7 or C7 and is spelled [ C E G Bb ].

This stuff is Fundamental Harmony and Fundamental Jazz Alchemy, as well.

Piano Players and most other melodic instrumentalists learn about these chords early in their training. I spent most of my formative years as a drummer. So, while I had a reasonably good grasp of rhythmic ideas, melodic and harmonic fundamentals were a complete mystery to me. I could hear it and appreciate it. But, understanding it from a compositional standpoint just wasn't there.

I was close to 30 when I encountered the Major 7, Minor 7, Dominant 7, and Min7b5 chords and fingerings in a book by Alan De Mause titled Guitar Power. Alan De Mause is deceased and his book is out of print. But, you may still be able to find a copy at a library or used at Amazon or Ebay.

The key thing that has stayed with me from this book is that you can take these formulas and key fingerings for the Guitar and harmonize practically anything. For me, it pretty much opened up the World of Chord Progressions.

Another book which accomplished something similar with triads and proved to be quite useful for working with triads to harmonize melodies was the George Van Eps Guitar Method by George Van Eps. This book may still be in print or superceded by a newer revision or update through Mel Bay Publications.

Both are important books. However, of the two, Mr. De Mause's book really keyed me in to Seventh Chords and their importance in the World of Jazz.

We've only scratched the surface on Jazz Chords and Jazz Harmony.