It’s a bit shame that I just start to learn music theory of guitar chords after FIVE years since I picked up guitar. In this post I will share how I have learned guitar chords from beginning.
1. know mappings from alphabets to do-rei-mi-fa-so-la-si
C is DO, D is REI, E is MI, so on so forth.
2. know every note on the neck of a guitar.
Ask yourself questions such as, what is the note on the 2nd fret on the 6-th string? How about the note on the 12th fret on 3rd string?
This page might be helpful: http://basicsofguitar.blogspot.com/2009/07/how-to-know-your-fretboard-well.html
3. know what is a major scale?
A major scale is a scale that starts from some note, from which the following notes have fixed intervals.
The so called fixed intervals are:
full, full, half, full, full, full, half
full = 2 semi-tone, half = 1 semi-tone
For example,
C C# D D# E F F# G G# A A# B C ... D♭ E♭ G♭ A♭ B♭
In the first line, C, C3, D, D#,…..,A, A#, B make up a chromatic scale. (A chromatic scale, by definition, contains 12 notes with semitone as interval.) An octave is the range from the first C to the next C, which spans 12 semitones. Physically, the frequency of a note is half as the frequency of the note in the next octave.
C, D, E, F, G, A, B are the notes in C major scale. Because D is 2 semi-tones higher than C, E is 2semi-tones higher than D, but F is 1semi-tones higher than E, so on so forth, which is exactly the intervals we said before: full, full, half, full, full, full, half.
On the second line, we list D♭, E♭, G♭, A♭ and B♭ because D♭ is the same note as C#, E♭ is the same note as D#, G♭ is the same note as F#, so on so forth.
good references to learn scale:
http://basicsofguitar.blogspot.com/2010/04/how-to-figure-out-notes-for-major-scale.html
http://musictheorysite.com/major-scales/list-of-all-major-scales
4. I believe people remember notes on the guitar neck based on the C major scale. That is, the open strings from the 1st to 6th strings are called E, B, G, D, A and E. So we will just use this scale from now on.
5. A chord often consists of three notes, which are called triads.
The first triad is called the root. The first letter in a chord denotes the root of this chord. For example, Cmaj means this is the major chord, with the root as C. Similarly, Amin denotes the minor chord with the root as A. The second triad is called the third. The third often determines the type of this chord (whether it is a minor or major or something else.) The third triad is called the fifth.
A major chord contains the triads with 4 semitones interval between the root and the third, and with 3 semitones interval between the third the fifth. A minor chord contains the triads with 3 semitones interval between the root and the third, and with 4 semitones interval between the third and the fifth.
So looking at the following scale again.
C C# D D# E F F# G G# A A# B C ... D♭ E♭ G♭ A♭ B♭
Cmaj will be a major chord consisting C(root), E(the third), and G(the fifth) because E is 4 semitones higher than C and G is 3 semitones higher than E.
Cmin will a minor chord consisting C(root), D#(the third) and G(the fifth) because D# is 3 semitones higher than C and G is 4 semitones higher than D#.
Besides major and minor chords, there are other types of chords. Please see more info below. These are the websites I am referring to along the way I learned chords.
http://www.essentialguitar.com/
http://www.fretjam.com/guitar-chord-theory.html
6. After learning these, all you have to do first is to memorize all major chords rooting at different notes. Then, if you are asked to give other types of chords with same root, you can just move your finger accordingly from the major chord.