01. What’s A Chord?
As an introduction, let me explain what a chord is – if you’re confident you know, skip this paragraph. A chord consists of three notes, which we will call I, III and V. Note I is called the root, and is the letter the chord will follow: for example, the root of D major is D, the root of E minor is E. Note III affects the key of the chord, and is a “third” which is either “minor” or a “major”. These are placed three and four semitones (frets) above the root to determine the key of the chord: for example, the III in D major is F# and the III in E minor is G. Note V, meanwhile, is seven frets above the root, except when it isn’t, but we won’t worry about that yet. In our examples again, note V in D major is A, and note V in E minor is B.
On a piano, major chords can be played as simply as above – just count up four from a desired note, and then another three from that, and play all three keys. I prefer to think of it as two separate sums: I + 4 and I + 7. On a guitar, it isn’t so simple – you have to make each string play something relevant, or at least not wrong, to the chord you want to get going.
02. Constructing The Most Common Chords
Let’s construct a D major chord, as used extensively in Sixpence None the Richer’s song “Kiss Me” among many, many other things – it’s a pretty common chord that you might already know, but let’s pretend you don’t.
The 0 on the D string is a D note, which I expect you to already know. Let’s say, then, that you just played open strings after that. You would be playing D, G, B and E, and while this is technically an Em7, that isn’t really what you were planning on – you need D, F# and A, and nothing else. Now, the D is fine, but the G is going to have to go – by fretting it at the second, you can get an A instead. The B isn’t any good either – turn it into a D by fretting it at the third. You still need an F#, and you can get one by playing the second fret of the E string. Once you’ve got all these notes down, strum the strings and you’re playing a D major chord:
D major: xx0232
Let’s say you want to play a D minor instead – this chord can be found in a lot of sadder songs, including Opeth’s “Drapery Falls” at 7:57. I and V are the same in Dm as they are in Dmaj, so you can leave all your Ds and As where they are. The F# is going to have to go, though: you can turn it into an F by moving it down one fret. So your D minor chord, then, is:
D minor: xx0231
There are other types of chords as well, and while I don’t consider them to be as useful, it’s never bad to learn them in theory. A diminished chord uses a minor third, like Dm, but also a note called a diminished fifth, which is six semitones (rather than seven) above the root. In D, this means D + F + Ab. Make the D minor shape again, and keep both the Ds and the Fs there, but flatten the A one semitone (i.e. slide it one fret back) to make Ab. You might need to refinger this for comfort – that’s absolutely fine.
D diminished: xx0131
The counterpart to the diminished chord is the augmented chord, which uses the major third (like D major) but another note called an augmented fifth, which is eight semitones (again, rather than seven or six) above the root. In D, this would be A#. You know how to play a D major, so do that, and then take the A (2nd fret G, remember) and move it one fret up to give you D augmented:
D augmented: xx0332
Use of augmented and diminished chords aren’t so common in popular music, but you do get the odd track that uses one, and they’re definitely funky sounding things to play around with. To hear an augmented chord in use, check out Zappa’s “Muffin Man”. For a good example of fun with diminished chords, try the Dresden Dolls’ “Girl Anachronism”.
03. Seventh Chords
Far more common are things called seventh chords. These are useful for various harmonic purposes that I’m not going to talk about here, but you might want to bear in mind that used often they tend to sound quite jazzy, especially minor 7s. These introduce a whole new note to the chord pool, the seventh. This means you’ll be playing, basically, four notes instead of three. It’s worth noting that sometimes, this will be very inconvenient to do: at such times, you drop a note you’re playing twice, if you can, or the fifth, if you can’t.
There are two varieties of seventh note, which are the major and minor seventh. You can work these out by counting one or two semitones down from the root respectively. (Or you can count up 10 for minor sevenths and up 11 for major ones, but that would take much longer). In D, the minor seventh is C, and the major seventh is C#.
There are, then, four varieties of seventh chord, because there are four combinations of thirds and sevenths you can have. Here’s a little table I made that tells you about each one:
root + minor third + minor seventh = minor seventh chord
root + major third + major seventh = major seventh chord
root + major third + minor seventh = dominant seventh chord
root + minor third + major seventh = minor major seventh chord
Let’s start with a minor third and a minor seventh: in D, this will give you a chord called D minor 7. This chord is used in the song Autumn Leaves, a jazz standard played by many, including Miles Davis. Starting at D minor won’t give you any wrong notes, but you’ll be missing the C. If you’re constructing a chord and this happens, work out which of your notes can be changed – in this case, we already have a D on the open string, so we don’t really need another one on the B string. This note can be changed for the C we need by moving it back two frets, giving you:
D minor 7: xx0211
Next we have the major seventh chord, constructed of the root, the major third, and the major seventh. Get a D major chord down, and, since you’ll have the same problem as in the minor 7 chord with your missing seventh, move the D back only one fret, and you’ll have a D major 7:
D major 7: xx0222
The dominant seventh chord is also known as simply a “seventh” chord, and works in pretty much the same way as the others. Harmonically, this chord “wants to” go to a G – D, the root, is the fifth of G, and a dominant 7th chord is a more interesting way of getting between the two. This might be worth bearing in mind if you want to get between the two, but isn’t really worth worrying about for the purposes of this lesson. Anyway, start at D major, then get the minor 7th by moving the D on the B string back 2 notes, giving you D – A – C – F#
D dominant 7, aka D7: xx0212
I don’t much see the use in telling you how to construct a D major-minor 7, as you should be able to work it out yourself by now already, and since I don’t really know what they’re for I’ll just write it out:
D major-minor 7: xx0221
That’s it for the more important, widely used chords (since power chords are not, technically, chords, but constructions that only use notes V and I – easy enough to work out) but what about other, less widely-used chords? What about sus4 chords, like in Bohemian Like You by the Dandy Warhols? What about 9th chords, like in the Police’s Every Breath You Take? What about jazzy 9ths? What about chords with roots other than D?
Well, chords other than D are easily worked out in the same way, you just start on a different note. I just picked on D because it’s easy to only deal with four strings each time. Say you want A – well, find an A note on your guitar, and make each string do something useful, and you’ve got it. Try going through the first part of the lesson again constructing each chord using A as the root rather than D, if you fancy an exercise. You can do this again for C, G and E as well.
04. Less Common Chords
As for sus4s, 9s, add11s, add13s, etc, you’re basically adding a note that’s referred to in the chord name. A sus4 simply means you add a suspended fourth. I don’t know where the “suspended” comes into it, but you just add the fourth (IV) to the chord. So, like in Bohemian Like You, Dsus4 would simply be xx0233, with the fourth (G) replacing the third (F#). These work in the same way as sevenths, in that you just add them to what you’re already playing without losing anything, if you can, and if you can’t, lose a note at your discretion. For more on this, or to clear up any uncertainty, try the other lesson on chord construction on ultimate-guitar.com, which has plenty on all sorts of strange chords you might like to learn.
05. Barres
With this knowledge at your fingertips, you can construct just about any chord with the roots C, A, G, E and D. There are, of course, seven other keys which need roots, and for those, you’re going to be dealing with barre chords. In case you don’t already know, barre chords refers to the technique of putting one finger across multiple strings. This is useful, and perhaps necessary, for playing hard-to-reach chords like, for example, B major.
To play a B major (B-D#-F#) in open position, you’d have to do this
Weird B: x21402
This sounds a bit rubbish, because 4 and 0 are (theoretically) the exact same note (although they will be slightly off due to tuning, string tension, timbre, etc), but it’s just as likely it sounds rubbish because it’s hard to play. What if it wasn’t? What if you could just take a simple shape like that of A major (x02220, fact fans) and make that equal B instead?
Well, you can. That’s what barre chords are good for. If you imagine that open strings are a fret of their own (fret zero) then a barre chord effectively moves your “fret zero”. By placing your index finger across all the strings at the second fret, for example, playing all strings “open” means you get F# - B – E – A – C# - F# rather than E – A – D – G – B – E. So what? So, any chords you play on top of this barre will be transposed up two semitones. Get your A Major shape with your other three fingers (or just one, if you prefer) and place it on the fourth fret, and you’ve got a B Major chord. You could even move the entire thing, including the barre, up another fret and be playing C major. A fret up from that would be C# major, and so on, and so forth.
You can play any of the C – A – G – E – D rooted chords on top of a barre in the same way you play them on top of open strings, and the chord pitch will be transposed by however many frets up you’ve stuck the barre. For example, if you take an E minor chord and put it on top of the second fret barre I talked about just now, you’ll be playing an F# Minor chord, because F# is 2 semitones from E. The shape of the chord doesn’t need to change, and you can continue to think of it as an E chord if you prefer when adjusting the notes to make another kind of chord (eg a seventh).
That’s pretty much it for chords. Hopefully, you’ve learnt how to construct just about any one you like, though you’d have to read a bit on harmony to work out exactly what one it is you’re after. The other result I hope this lesson has had is that you’ll be able to give correct names to chords you’ve played when messing around which might give you ideas for progressions when put with your existing theoretical knowledge.
/ my profile 
Very cool. check out www.guitarroadmap.com for when and where to use certain chords.