Chords - Music Theory

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Intervals

To understand chords, we must first take a close look at intervals.

Interval - The space between two notes.

A chord has to have a minimum of 3 notes, called a chord triad. A chord triad consists of 2 intervals. The smallest interval in western music is the half-step. On a piano keyboard, this would be playing 2 notes without any other notes in between them. B - C, C - C#, E - F, Gb - G, are all examples of half-step intervals.

The next largest interval is the whole step. A whole step consists of 2 half steps. B - C#, C - D, E - F#, Gb - Ab are all examples of whole step intervals.

The next largest interval is the minor third. A minor third consists of 1 1/2 steps. The interval which is larger than the minor third is the major third, which consists of 2 whole steps (or 4 half steps).

The following chart shows the intervals starting from G.

IntervalName
G - Abhalf-step
G - Awhole-step
G - Bbminor third
G - Bmajor third

* There are more intervals than the ones listed, but for purposes of learning chords, only the half-step, whole-step, minor third and major third intervals will be covered.

There are only 4 types of chord triads; major, minor, augmented and diminished. These chords are defined by their intervals.

The following is a chart of the various G chord triads, with the notes of the chord and interval names listed:

G ChordNotes of ChordOrder of Intervals
G MajorG B DMaj-3rd Min-3rd
G MinorG Bb DMin-3rd Maj-3rd
G AugmentedG B D#Maj-3rd Maj-3rd
G DiminishedG Bb DbMin-3rd Min-3rd

Knowing the intervals which make up chords, will allow a person to find chords without any additional aids.

Seventh Chords

If we extend the chord triad by giving it a fourth note, we get 7th chords. The following chart lists the most common 7th chords for G along with the appropriate intervals:

G 7th Chord Notes of ChordOrder of Intervals
G Major 7G B D F#Maj-3rd Min-3rd Maj-3rd
G Dominant 7G B D FMaj-3rd Min-3rd Min-3rd
G Minor 7G Bb D FMin-3rd Maj-3rd Min-3rd
G Half-Diminished 7G Bb Db FMin-3rd Min-3rd Maj-3rd
G Diminished 7G Bb Db EMin-3rd Min-3rd Min-3rd

You may want to go further and chart out the intervals for 5, 6 and 7 note chords as well. I will not go any farther than charting 4 note chords.

Applying chords to music

To apply chords to music, first find out the key of the song. Then by harmonizing the corresponding scale, or simply using the number system, one can find all of the chords which work for a given key.

An example would be if a song is in the key of A major, it scale would be:

  • A B C# D E F# G#

Any chord which contains notes derived from this scale will work in this key. So, A major 9 (A C# E G# B) works since all it's notes are derived from the A major scale. Db major (Db F Ab) won't work within the key. But try it anyhow, it may work in the song even though it doesn't fit the key. Don't be afraid to place chords in a song which aren't derived from it's key(s). In other words, don't limit yourself to the key of a song/progression. Keys are to be thought of as guidelines.

Chord naming conventions

Let's use chords derived from the C major scale as examples:

C D E F G A B

Chords are derived from numbering the scale degrees of the corresponding root. (C=1, D=2, E=3, etc.). When the notes of the scale go into another octave, the numbers continue.

C  D  E  F  G  A  B  C  D  E   F   G   A 
1  2  3  4  5  6  7  8  9  10  11  12  13

A chord triad will contain the 1, 3 and 5. A Seventh chord will be numbered, 1, 3, 5, 7. Here is list of the basic chord names and their corresponding numbers:

Number of notesName
1 3 5Triad
1 3 5 7Seventh
1 3 5 7 9Ninth
1 3 5 7 9 11Eleventh
1 3 5 7 9 11 13Thirteenth

Notice the pattern. The notes of all chords (except suspended and 6th chords) are derived from choosing a tonic, and building the rest of the notes from the corresponding scale by skipping every other note of the scale.

Naming Chord Triads

Earlier, I demonstrated how to find the name of chord triads using intervals. The chart below illustrates how a chord name can be found by examining the numbers of the major scale in which it is derived from.

C Chord Triad Notes of ChordNumbers of Chord
C MajorC E G1 3 5
C MinorC Eb G1 b3 5
C AugmentedC E G#1 #3 #5
C DiminishedC Eb Gb1 b3 b5
Suspended Chords
A chord which has its third either raised to the 4th or lowered to the 2nd scale degree.

C F G = C sus 4 (sus 4 chords are usually written without the "4", i.e., "C sus"

C D G = C sus 2

There has been some confusion about suspended chords. I once saw a chord labeled as a Minor sus 4. This is an erroneous name because by definition, a suspended chord has no third, but a minor chord has to have a flatted third. The intended chord was a Minor add 11 chord.

The following is a list of most, if not all, of the possible C chords and their corresponding names.

Notes of ChordChord Name
C E GC Major
C Eb GC Minor
C E G#C Augmented
C Eb GbC Diminished
C Eb Gb BC Half-diminished
C Eb Gb BbC Diminished 7
C F GC Suspended 4
C D GC Suspended 2
C F G BbC Suspended 7
C F G Bb DC Suspended 9
C F G Bb D FC Suspended 11
C F G Bb D F AC Suspended 13
C E G BC Major 7
C E G BbC Dominant 7
C Eb G BbC Minor 7
C E G AC Major 6
C Eb G AC Minor 6
C E G A DC 6/9
C Eb G A DC Min 6/9
C Eb G BC Minor/Major 7
C E G# BC Maj 7 Sharp 5
C E G# BbC Dom 7 Sharp 5
C E Gb BC Maj 7 Flat 5
C E Gb BbC Dom 7 Flat 5
C Eb G# BbC Min 7 Sharp 5
C E G Bb D#C Dom 7 Sharp 9
C E G Bb DbC Dom 7 Flat 9
C E G B DC Maj 9
C E G Bb DC Dom 9
C Eb G Bb DC Minor 9
C E G# B DC Maj 9 Sharp 5
C E G# Bb DC Dom 9 Sharp 5
C Eb G Bb DbC Min 7 Flat 9
C E Gb B DC Maj 9 Flat 5
C E Gb Bb DC Dom 9 Flat 5
C Eb G Bb DC Min 9
C Eb Gb Bb DC Min 9 Flat 5
C Eb G B DC Min/Maj 9
C E G B D#C Maj 9 Sharp 5
C E G B DbC Maj 9 Flat 5
C E G Bb D#C Dom 9 Sharp 5
C E G B DbC Dom 9 Flat 5
C E G# B D#C Maj 7 Sharp 5 Sharp 9
C E G# Bb D# C Dom 7 Sharp 5 Sharp 9
C E G# B D#C Maj 7 Sharp 5 Flat 9
C E G# Bb D#C Dom 7 Sharp 5 Flat 9
C E Gb B D#C Maj 7 Flat 5 Sharp 9
C E Gb Bb D#C Dom 7 Flat 5 Sharp 9
C E G B D FC Maj 11
C E G# B D FC Maj 11 Sharp 5
C E G B D# FC Maj 11 Sharp 9
C E G# B D# FC Maj 11 Sharp 5 Sharp 9
C E Gb B D FC Maj 11 Flat 5
C E G B Db FC Maj 11 Flat 9
C E Gb B Db FC Maj 11 Flat 5 Flat 9
C E G Bb D FC Dom 11
C E G# Bb D FC Dom 11 Sharp 5
C E G Bb D# FC Dom 11 Sharp 9
C E G# Bb D# FC Dom 11 Sharp 5 Sharp 9
C E Gb Bb D FC Dom 11 Flat 5
C E G Bb Db FC Dom 11 Flat 9
C E Gb Bb Db FC Dom 11 Flat 5 Flat 9
C E G Bb D F AC Dom 13
C E G B D F AC Maj 13
C E G Bb Db F AC 13 Flat 9
C E G Bb D# F AC 13 Sharp 9
C E G Bb D# F AC 13 Sharp 9

* "Dom" is an abbreviation for Dominant. All 7th chord names without the "Dominant" or "Major" qualifier (C 7th) are implied to be Dominant seven chords. "Half-diminished" is also called "Minor 7 flat 5". "Augmented" is an alternative name for any chord with a sharp 5. Ex; C Dom 7 Sharp 5 = C Augmented 7

The names of the chords are cumulative. In other words, if a chord is called a ninth, it must contain all of the triad numbers below nine. An eleventh chord must contain 1 3 5 7 9 11 in order to be called a true "eleventh" chord. If a chord does not hold to the pattern, say the alleged eleventh is missing the 9, containing 1 3 5 7 11, then it is said to be a "seven add eleven". For instance, C E G B F is a C major 7 add eleven, while C E G B D F is a legitimate C major eleven chord. Here are some more examples:

Notes of ChordChord name
D F# A ED major add 9
Eb G Bb Db F CEb Dom 7 add 11 add 13
G B D C EG major add e11 add 13

Inversions

The best way to define inversion is to illustrate them:

The C major triad has three inversions:

  • C E G - root inversion
  • E G C - 1st inversion
  • G C E - 2nd inversion

C Major 7 has four inversions

  • C E G B - root inversion
  • E G B C - 1st inversion
  • G B C E - 2nd inversion
  • B C E G - 3rd inversion

C G B E is not an inversion. All the notes of the chord must be present and no note can be skipped, only the sequence of the notes can be altered in a chord inversion.

Voicings

A chord voicing is different from a chord inversion in that a note can be skipped or repeated in a chord voicing. Again, the best way to teach about chord voicings is to illustrate them:

C G B E is a chord voicing of C major 7.

C B E G is a chord voicing of C major 7

G C E G is a chord voicing of C major 7.

C G C B E is a chord voicing of C major 7.

B G E C E is a chord voicing of C major 7.

As chords get bigger (elevenths and thirteenths), most musicians will tend to drop one note of the chord. Usually, (this is not a rule) the eleventh is the first note to go in a thirteenth chord, thus technically making the chord a 9 add 13 (assuming no other note is dropped).

One thing to keep in mind about voicings and inversions is that with bigger chords, voicings/inversions become increasingly important as to how the chord sounds. For instance, for the G major 7 chord, voiced G B D F#, this chord can sound "jazzy", while voiced B D F# G is too disonant because of the F# and G being placed right next to each other. The latter voicing is a rarely used one for this chord.

Alternate names for chords

In the notes above, I talked about some alternate names for chords (Half-diminished/Minor 7 b5 is one example). But some chords have alternate names which can be chosen based upon how the chord is being used within the context of the song/progression. Some examples are:

Notes of ChordChord NameChord Name
A C E GA minor 7C major 6 (3rd inversion)
B D F AB half-diminishedD minor 6 (3rd inversion)
G C DG suspended 4C suspended 2 (1st inversion)

Augmented chords have 3 possible names, usually chosen based upon which inversion is being used:

Notes of Augmented ChordChord Name
C E G#C Augmented
E G# CE Augmented
G# C EG# Augmented

So, which name should be used in which situations? Whichever is easiest. But, a general rule of thumb is that the note in which the bass note (played by a bass player or left hand of piano) is playing, is usually the root of the chord in question. So, if a B D F A is being played over a D bass note, then it is probably best to call this chord a D minor 6. Of course if the bass note is an F, A, G or other note besides B or D, this rule cannot be applied.

Polychords

Polychords are technically two or more chords put together. But most, if not all polychords are really part of a bigger chord. For example:

  • C E G B D = C major 9

Consists of:

  • C E G = C major
  • G B D = G major

I think of polychords as another way of thinking about large chords. As chords get bigger, it can be easier to think of them as consisting of two or more smaller chords. This is especially true for piano players.

Here is a list of a few polychords and their "real" chord names.

Notes of polychordPolychord"Real" name
B D# F# AB Major/D# DimB Dom 7
D F# A C ED Major/A MinorD Dom 9
E G B D F#E Minor/B MinorE Min 9
C E G Bb EbC Major/Eb MajorC Dom 7 Sharp 9

Thinking in terms of polychords can also help with orchestration. For instance, with many instruments, one could orchestrate the piano to play a C Major and the guitar to play an Eb Major (1st inversion), thus together they are playing the C Dom 7 Sharp 9 chord (see above).

Powerchords

Powerchord
A "chord" (see note below) which contains no 3rd (suspended chords, and chords containing 3 or more notes exempted)
Notes of power chordChord Name
C GC 5 (or C power chord)
G DG 5 (or G power chord)
E B EE 5 (or E power chord)

>* NOTE: Technically, a powerchord is not really a true "chord" because, by definition, a "chord" has to have a minumum of 3 notes. Powerchords are also called "5" chords, notated as C 5.

Powerchords are neither minor or major and therefore either scale can be used over top of them. Only when a scale is used over them, is a major or minor tonality implied to the listener. Therefore, one can easily alternate between being in a major key or minor key (thus using chords which are derived from either number system).

The following chord progression illustrates this:

C 5, F Major, G Dom 7, C5, Bb Major, Eb Major

When examined, the first three chords of this progression, are derived from the key of C Major, while the last three chords are derived from C minor, for C Maj, F Maj and G Dom 7 are the I, IV and V chords of C *Major*, while C Min, Bb Maj and Eb Maj are the i, VII and III chords of the key of C *Minor*.

The blues scale works very well over these types of progressions being that it contains both the minor and major third in it. A blues scale contains both the Eb of C minor and E of C major. One could also simply play the C major scale over the first 3 chords, and then transition to the C minor scale for the last 3 chords.

Power chords are especially popular among rock and blues music. The power chord is used a lot by guitar players because the guitar's standard tuning and the distortion's effect upon the sound of the major third.

Slash Chords

    Slash Chord
    The combination of playing a bass note with a chord.

C Maj/Bb is the notation for the C major chord being played over a Bb bass note. The Bb note is not found within the C major chord, but together, this slash chord is a C Dom 7th. My favorite slash chord is the Bb Maj/C because it is an excellent substition for the C eleventh chord.



Additional Resources

Chords | Learn chords without reading music | The melodic minor scale and the dominant seventh flat9 (V7b9) chord


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