Thursday, June 7, 2007


Chords are used to accompany single melody lines. This is often done by an instrument capable of playing chords (e.g. a keyboard or guitar) or else by several instruments or voices added together to form chords (e.g. a band or choir). I mentioned above that the I chord (or tonic), can sound "at rest". Other chords can often sound as if they want to change, either back to the tonic or to a different chord. This is because there is a certain amount of tension, either because they are simply not the tonic chord, or else because the notes within the chord create tension with each other. The use of tension (and it’s subsequernt release) is a very important part of music, either in adding interest or creating emotions as the chords move from one to another. When you add harmony to an existing melody, you need to think of two important things
The chords must fit the melody. This means that significant notes of the melody are notes of the current chord.
The chords often move from one to another in a way that helps to create tension and release, or interest. You can think of a chord sequence or progression as a musical journey.
To get a good idea of this you must play and listen to the chords. I suggest you get hold of a keyboard and start learning where the notes are. You don’'t need to be a virtuoso pianist, but you must be able to play chords, even slowly, if you are going to learn music theory.
First of all play a C triad followed by a D triad uusing the charts above to work out the notes. You will hear that whereas the C sounds like "home", the Chord on D sounds like you have gone somewhere else. This is the start of a journey.

This D chord is in fact a minor chord, and all chords built on II of a major key are minor chords. What defines it as a minor chord is that unlike the C major, the musical interval (or difference in pitch) between the root and 3rd is smaller. It is made up of a whole tone and a half tone (a.k.a. a minor 3rd). The interval between the root and 3rd of a C major chord is made up of two whole tones (a.k.a. a major 3rd). From now on I am going to use a small "m" to denote a minor chord so we will call this Dm or IIm. In classical harmony it is common to use lower case roman numerals to denote a minor, I prefer to use the capitals and add the small "m" as it fits in with standard pop and jazz chord symbol notation.
Possibly most important chord change is from the V chord to the I chord, ie G to C in the key of C. This is called a perfect cadence and usually happens at the end of a tune, and also at the end of a phrase within the tune. I mentioned above that when you go from a C chord to a D minor chord it is like the start of a journey. If C (chord I) is home, D minor (chord II) is setting off somewhere else. The G chord (chord V) is the journey home so it is very useful that this chord has the most tension waiting to be released when you finally arrive home.
I mentioned before about tension within the notes of a chord. The V chord (called the dominant chord) is a very good example of this, but first we need to extend the chord. So far we have been looking at three note chords, or triads. The same principle of creating the chords is involved. We are now going to make a four note dominant chord. This is particularly useful because even with music that uses simple triads, more often than not the V chord is extended to a four note chord to take advantage of the extra tension that this chord is capable of when it is most often needed: the final cadence.

Creating a Four-Note Chord
Following on from our method of creating triads, to make a four note chord we just continue counting up the scale from the root of the chord. So if the root is G, we count up the C scale from G and use the alternate notes: root, 3rd and 5th as with a triad, but continue one more step: miss out the 6th note and add the 7th:

To differentiate between this and a G triad we call this a G7 chord. In this particular chord (along any V7 chord of whatever key), the interval between B and F (known as a "tritone" as it is made up of three whole tones) is one that has a lot of tension. This used to be called the devil’s interval as it was considered very dissonant. These days our ears are more used to such dissonance. Play this chord on the keyboard, then play just the tritone. You will easily hear how the B seems to want to resolve the tension by moving up to a C, and the F wants to resolve the tension by moving down to the E. Guess what? These are the most significant notes of a C major triad: the C because it is the root and tonic of the key, the E because that is what defines it as a major type of chord. So not only have we just created tension by adding a note (the 7th) to a chord, we created extra tension because that particular note sets up a certain amount of dissonace within the chord, and this tension finds release by progressing to the tonic chord and so completing that journey (or part of a bigger journey):

Count Notes Chord
7th F F
6th E
5th D D
4th C
3rd B B
2nd A
1st G G

Home Set off somewhere Journey back Safely Home
Chord I (C) Chord IIm (Dm) Chord V7 (G7) Chord I (C)

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