Chord Theory Part 1

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Melody is a group of notes played in succession.  Harmony is a group of notes played at once.  Many theorists break this up into thinking horizontally (melody) and vertically (harmony). 
  
The basic unit of harmony is the chord.  A chord is composed of three or more different notes played at the same time.  Two notes together make an interval, or power chord, but to have a true chord, you need at least three notes, though they need not be played on the same instrument. 
  
The most pleasing consonant interval is the third, either major or minor.  All chords can be though of as some combination of stacked major and minor thirds. 
  
The simplest type of chord is called a triad.  It is composed of three notes: two thirds stacked on top of each other.  Since there are two types of thirds, this yields four different combinations – four types of triads.  From most common to least: 
  

  
M3 + m3 
  
m3 + M3 
  
m3 + m3 
  
M3 + M3 

  
Major triad 
  
minor triad 
  
diminished 
  
Augmented 

  
C E G 
  
C Eb G 
  
C Eb Gb 
  
C E G# 

The first note is the root of the chord, the base tone.  The second note is the third because it is a third up from the root.  The third note is the fifth.  Notice that in the major and minor triad, the distance between the root and fifth is the same.  This interval is known as a perfect fifth. 
  
In the diminished chord, the fifth is flat by a half step, a diminished fifth (b5).  The interval is one fret lower than a perfect fifth.  The diminished triad can be thought of as more minor than minor.  It is the only triad that contains the tritone, the most dissonant interval in western music.  Diminished triads are traditionally played inverted to hide the dissonance of the tritone. 
  
On the other hand, the Augmented triad has a fifth that is one fret higher than a perfect fifth.  This is known as an Augmented fifth.   You might recognize this interval as a minor sixth.  The notes are the same, but since the G# is functioning as the highest note in a triad, it is called a fifth in this situation. 
  
Spelling Triads 
  
We can get the basic triad spellings from the C Major Scale: 
  
C D E F G A B C 
  
If we start with each degree and add a third and fifth from the scale, we get the following triads: 
  

  
CEG 
  
 DFA 
  
 EGB 
  
 FAC 
  
 GBD 
  
 ACE 
  
 BDF 

  

  
 ii 
  
 iii 
  
 IV 
  
 V 
  
 vi 
  
 vii_ 

  
The capital numerals are major triads; the lowercase numerals represent minor triads, and the (_) means a diminished triad.  Augmented triads do not appear naturally in the diatonic modes. 
  
Notice there are three basic groups of spellings: 
  

  
Major 
  
 minor 
  
 diminished 

  
CEG 
  
 DFA 
  
 BDF 

  
FAC 
  
 EGB 
  
 
GBD 
  
 ACE 
  

  
The first group is Major when it appears without sharps or flats.  Flatting the third of these chords (C Eb G for example) spell minor triads. 
  
The second group is minor without sharps or flats.  If you sharp the third of these chords (D F# A), you spell the major triad of that root. 
  
The third group spells a diminished triad when it appears without flats or sharps.  Sharping the fifth (B D F#) will spell a B minor triad.  Sharping the third and the fifth (B D# F#) spells a B Major triad. 
  
Sharping the fifth of a Major triad yields an Augmented triad.  Flatting the fifth of a minor triad yields a diminished triad. 
  
Flatting or Sharping all the notes in a triad yields a chord with the same quality as the natural version of that spelling.  C# E# G# is a C# Major Chord.  Db Fb Ab spells Db minor.  Bb Db Fb spells Bb diminished. 
  
In spelling chords with flatted or sharped roots, removing a flat is the same thing as adding a sharp for a chord with a natural root.  Removing a flat is the same thing as adding a sharp.  C# E G# spells C# minor.  Db F Ab spells Db Major.  Bb D F spells Bb Major. 
  
Seventh Chords 
  
By stacking another third on top of a triad, we build a four-note chord with a Root (1), 3rd, 5th, and 7th.  The interval of the seventh has major/minor tonality. Obviously, this yields a lot more possibility than the three notes of a triad.  Not all of these possibilities are commonly used.  We can begin by thinking first of Major and minor triads, plus a Major or minor seventh. 
  

  
        Major 7th 
  
        minor 7th 

  
       Major triad 
  
        Major 7 
  
       Dominant 7 

  
       minor triad 
  
       minor/Major7 
  
       minor 7 

  

It is useful to know at least two moveable voicings of each flavor of chord: one with a root on the E string, one with a root on the A string.  This way, you will always be within three frets of any possible chord.  This is about the minimum necessary to accompany in real time with decent voice leading. 

 Major 7, M7, Δ7 
  
A major third stacked on a major triad ( C E G B ).  This is basically the sweetest chord in music.  It’s too jazzy and sweet to use often in rock, but a great tool to have when it’s called for.  A good example of it would be Red Hot Chilli Peppers’ “Under the Bridge” – the unaccompanied chord at the end of each verse. 
  
This is the home chord in most jazz tunes. 
  

  

minor 7, m7, -7 
  
This is a chord that will be among the most useful to rock musicians.  It is a minor third on top of a minor triad ( C Eb G Bb ).   It has a sort of passive melancholy character that’s good for vamps and ballads.  The vamp at the beginning of Van Morrison’s “Moondance” is made of m7 chords. 
  

Dominant 7, 7, Dom7 
  
If you see a letter with just the numeral “7" after it, this is what you play.  This is the V7 chord.  It is a major triad with a minor third on top of it ( C E G Bb). This chord has an overbearing dynamic character that says “resolve me – immediately.”  Blues progressions are commonly played with all dominant chords.  Notice that the Dominant 7 chord contains a tritone, or b5, between the third and seventh.  This is the source of the dissonance and dynamism. 
  
A V7 chord over a minor progression will suggest harmonic minor.  This is very useful for neoclassical shredder types.  It creates powerful, obvious resolutions, so it’s also useful for signaling changes in a jam band setting.    It comes up a lot in funk and blues-rock. Depending on how sappy or funky you are, there’s a good chance you may use this as much or more than the minor7. 
  
The theme of all music is basically conflict and resolution.  Resolution can be either Major or minor.  Conflict, however, is always Dominant.  This chord, and its variants, are the nexus of the need to resolve.  One could hypothetically replace the word “Dominant” with “dissonant” and not lose much information. 
  

  
As we will see later, there are many common substitutions for Dominant 7 chords. 
  

minor-Major7, m/M7, m(M7) 
  
The m/M7 chord is a minor triad with a Major third on top of it ( C Eb G B ).  This chord does not occur in the diatonic modes.  The minor third and major seventh play against each other in an ambiguous way, similar to a suspended chord.  It feels unresolved, but unlike the dominant chord, it is unclear where the resolution goes. 
  
Minor-Major7 is the tonic chord in harmonic minor.  Harmonic minor is powerful for its V7-i resolution.  It is common to shift back to aeolian or dorian for the tonic.  Bebop-oriented jazz musicians tend to stay in harmonic minor more often.  The most well-known uses of this chord are at the end of the James Bond theme and the beginning of Wagner’s Tristan and Isolde. 
  

  

Half-diminished, m7b5 
  
The half-diminished chord is a diminished triad with a minor seventh.  This chord is harmonized naturally from diatonic modes.  It implies locrian.  It is common as the ii chord in ii-v-i progressions in minor keys.  It can be thought of as a m7 chord with an altered (flat) 5th.  The chord has a funky, cosmopolitan quality, along with the melancholy of the diminished triad and minor seventh harmonies.  It is suitable for jazz and funk.  Although it’s tied to the locrian mode, it’s probably too bright for rock or metal. 
  

  
It is different from the dim7 in that the interval between the b5 and the m7 is a major third.  A dim7 chord is made of all minor thirds. 


  

 dim7, °7 
  
This is a diminished triad with a minor third stacked upon it.  Since all the intervals are smaller, the added note is a major sixth up from the root (B D F Ab, for example).  This chord is usually used as a substitute for the dominant 7, by superimposing it so that the tritones line up. 
  

  
Another commonly used device is to slide up the neck, playing diminished seventh chords separated by minor thirds.  This is sort of a rhythm player’s approximation of a long diminished arpeggio.  Because the chord is made of only one interval, inverting the chord will give you the same voicing. 
  

  
You can still get interesting voicings by spreading the notes through several octaves. 

  
  

Aug7, +7, 7#5, M7#5 
  
An Augmented triad is made of all Major thirds ( C E G# ).  Adding another Major third (following the pattern of the dim7) would take us back to the root. 
  
This leaves us with a philosophical question of which seventh to play, Major or minor.  There are many areas of music theory that are ambiguous, disputed, or unresolved.  The Aug7 chord is one of those areas. 
  
If you hear the Augmented triad as dominant, it would be reasonable to play the minor 7.  This chord would be spelled C E G# Bb.  Notice that this creates the interval of a major second rather than a third, between the fifth and seventh.  Also, this chord could be thought of as simply a dominant seventh chord with a sharp fifth (C7#5). 

  
If you want to continue the pattern of Major intervals, you could play the Major seventh.  This gives us C E G# B.  The interval between the fifth and seventh is a minor third.  This chord could also be named CM7#5 for more specificity. 
  

  
In disputed areas, it’s best to be pragmatic.  When rehearsing a standard, try both versions and make a note of which sounds best to you.  Reading in front of an audience, it’s smart to just play the triad to avoid an accidental m2 with another player. 
  
Writing your own tunes, it’s generally best to use a more specific chord name.  These chords can be written as altered 5ths, altered 13ths, or as a triad over a bass note, depending on the inversion and function in the song. 
  
An even simpler approach is to write “Aug,” and leave it to future players to determine if it needs a seventh or not.  Both versions of Aug7 are useful, but they both contain compromises in them that ultimately sound more subtle, less pure than the Augmented triad alone.  Don’t be lazy about it, but if you truly mean “Augmented,” rather than “altered,”  the triad is the best approach. 
  
Notice that the Augmented triad can be moved by Major thirds, similar to how the diminished triad may be moved by minor thirds. Also, if you want to get really fancy, you can move by the appropriate fifths. 
  

  
These are the fundamentals of being able to play and understand harmony in a sophisticated way.  You must know the four types of triads (M, m, Aug, dim), and the six most common seventh chords (M7, m7, 7, m/M7, m7b5, dim7).  Learn the common voicings, and make up your own to suit specific situations.  If you do this, you are well on your way to becoming a Good player.

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