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Chord Theory

You really should have a knowledge of Scales to appreciate chords, but its well worth it. Every scale has a set of 8 notes from the root note to the octave. You play these notes for scale practice don't you? (don't you?)

e.g. Scale of (or Key of) G is:


1 2 3 4 5 6 7 8
G A B C D E F# G

Chords start with the lowest note, called the root. So a G something chord starts with a G note and adds some higher notes. Two notes of a scale is known as an interval, the name of the interval being derived from how far apart the two notes are. Intervals were the first step towards harmony. Instead of a single melody, 2 voices would sing at intervals, giving a more expressive sound. It was realized as long ago as Pythagorus that certain intervals sounded pleasant and some did not. Pythagorus was probably the first to understand why. It is to do with the relationship of the frequencies of the notes. The pleasant ones became known as 'perfect' and have a simple frequency ratio relationship. There are only 4 perfect intervals - Unison, Fourth, Fifth and Octave. The other intervals are generally known as major or minor depending on whether the non-root note is the one in the scale or flattened by a semitone. Thus, in the scale of G, G-G is a perfect unison because they are the same note, G-D is a perfect 5th (5 notes apart G-A-B-C-D) G-C is a perfect 4th and G-g would be a perfect octave. On the other hand, G-A is a major second and sounds terrible - a discord. G-Ab, a minor second sounds worse. G-B is a major 3rd and sounds good. So does G-Bb which is a minor 3rd but sounds characteristically sad. G-E and G-Eb are a major and minor 6th and G-F# and G-F are a mojor and minor 7th.

Note that when a non-root note is sharpened, it is known as augmented, and when it is flattened, it is diminished. This means that G-Ab is both a minor 2nd and an augmented unison (since the other G in unison is sharpened by a semitone). This applies all the way through the intervals. G-D as well as being a perfect 5th, is also a diminished 6th. etc


1st note (root) 2nd note interval comment
1 1 unison two notes sound the same like the twin strings on a mandolin course
1 2 2nd An unpleasant interval. Usually taken as a discord and avoided except for effect
1 3 3rd a very important interval! It determines whether chords are major or minor
1 4 4th not much used
1 5 5th An interval that's usually present in any chord
1 6 6th A pleasant sounding interval
1 7 7th This one is straining to go up one to become octave
1 8 octave two notes sound the same but an octave apart