引文:

I'm sure many of us will know the circle of fifth principles. Just share some information I found. Please note these are just general concepts and may have many exceptions. But it is very useful and can be applied in many ways for a guitarist.

There is a piece of information about chord patterns that every guitar player ought to know. It summarizes all the information about how chords move from one to the next in a simple way. It's called the Circle of Fifths, and it's created by writing out the 12 notes in this order: each note is followed by the 5th note of its major scale. Thus, if we start with C, we follow it with G (the 5th note of the C major scale). We follow the G with D, which is the 5th note of the G major scale, and D is followed by A, and so on around the octave until we get to F, which is followed by C, and we're back to where we started. The complete Circle of Fifths looks like this:

---------------C
----------F-------- G
-----Bb/A#----------- D
--Eb/D#-------------------A
-----Ab/G#-------------E
---------Db/C#------B
----------------Gb/F#

There are two basic rules for chord changes. The first is that short movements along the circle sound more natural than long ones. For example, the chord change C major to G major is very natural, whereas the change C major to E minor is more awkward. The second rule is that clockwise moves (forward) make the song seem to be developing forwards, whereas counter-clockwise moves (backward) make the song be resolving. The chord changes we gave above are these:

C Am Dm G7 (Today). This one begins with a three-step jump forward, but then resolves back one step at a time.

F C7 F Bb F C7 F (When the saints go marching in). This one involves only single step movements. Starting on F, we go forwards, back, back, forwards, forwards, back.

Almost all chord movements in all songs involves jumps of 4 steps or less along the Circle, and most of them only 1 or 2 steps.

Using a certain chord in the circle as the tonic chord (I chord), moving clockwise will be the 5th chord (V or dominant chord), moving anti-clockwise will be the 4th chord (IV or subdominant chord). In key of C, the I, IV, V chords are C,F and G; in key of D, they are D,G and A, and so on. The I, IV and V chords together form the basic chords for many many songs. Examples are “Oh Susanna”, “Bye bye love”, “Cotton fields”, etc.