Keys and Chords

[DubGusset]

So i'm just learning about music theory; since i've always just played by ear.

If i choose to compose a song in a certain key; g for example. How would i know which chords can be played/composed using that key?

Thanks for any help,

Carey

[No name]

I've just begun to study this all myself not too long ago, so I will try to explain the best I can.

Let us say you did play in G major, and you wanted to use the chords in the key of G major. There are 7 in G. We use the position in the scale (which key your chord begins on, or "root note") to describe individual chords. They all use roman numerals. Lower case means "minor" and upper case means "major". A diminished chord uses lower case roman numerals with a circle shape at the end, augmented chord uses a upper case roman numeral with a plus sign at the end.

Using the major scale, (stick with the major scale, all the white keys, until you got all of this down).

The seven different chords are...

I ii iii IV V vi viiO (this last one is a dimished chord)

Each of these roman numerals corresponds to a particular degree of the scale, so...

I ii iii IV
Tonic Supertonic Mediant Subdominant

V vi vii0
Dominant Submediant Leading Tone


So in G it is as follows:

I=G,B,D
ii=A,C,E
iii=B,D,F#
IV=C,E,G
V=D,F#,A
vi=E,G,B
vii0=F#,A,C

These triads (3 notes:root,the 3rd, and the 5th;let us take triad I for instance. G is the root note, B would be a 3rd above the root note (and if you are counting intervals, a major third would be 4 half intervals above the root), and D would be your fifth (and once again if you are counting half intervals, it would be 7 half intervals above the root, unless of course it is the dimished chord, which in that case the fifth is lowered half an interval for a total of 6 half intervals).

Let me know if you need more clarification, as I know it got a bit deep here.

[Toxikator]

Easier way to remember: If you want to stay in key, stay in key.

Sounds silly, but if you're in G (Major) then you would just build your chords out of the notes of the G Major scale.

A traid chord is composed of "every other note" stacks (to simplify it). So if you're in G and you want to play the chord "G" you just sound G (skip A) B (skip C) D. GBD, there you go.

Two notes up from there? No problem. B (skip C) D (skip E) F#. BDF#.

Not so hard.

[No name]

Or that. I figured it would better to understand the rules behind it though, which is why I went in to so much detail.

[guitargeek9]

you need to get a teacher. you cannot possibly teach yourself theory the right way, get an instructor for a couple of months. sooner or later your going to have a question that even a forum can't answer

[Barf]

'When it sounds shit, it doesnt fit'

[Toxikator]

you need to get a teacher. you cannot possibly teach yourself theory the right way, get an instructor for a couple of months. sooner or later your going to have a question that even a forum can't answer

bullsh*t.

I learned (nearly) everything I know about theory from self research, and at the very LEAST all of the basics. I took several years of formal theory but almost all of my learning came from a textbook (not a teacher), information I could have gathered myself (had I not needed the credits for scholastic reasons.)

[No name]

Me too. It's not easy, but with plenty of studying and some help from folks on here at KVR you shouldn't have too much of a problem. Practice and study are vital of it.

[Deric]

you need to get a teacher. you cannot possibly teach yourself theory the right way, get an instructor for a couple of months. sooner or later your going to have a question that even a forum can't answer

guitargeek9 - Sorry, but you shouldn't tell people things like that. Some of them might just believe you and be seriously put off learning.

Your response is simply untrue. Why do you think he was asking in a 'Music Theory' forum?

DubGusset, No name and Toxicator are giving you good advice. Have a think about it, try and build the chords and scales as suggested, and then ask any more questions that may arise.

Oh, and good luck!

[Barf]

you need to get a teacher. you cannot possibly teach yourself theory the right way, get an instructor for a couple of months. sooner or later your going to have a question that even a forum can't answer

guitargeek9 - Sorry, but you shouldn't tell people things like that. Some of them might just believe you and be seriously put off learning.

Good point.

[k-bird]

So i'm just learning about music theory; since i've always just played by ear.

If i choose to compose a song in a certain key; g for example. How would i know which chords can be played/composed using that key?

Thanks for any help,

Carey

Here's an explanation that involves the least amount of theory possible and works with any diatonic eight note scale.

We'll go with your example, G. The notes in G are G A B C D E and F#, and of course this wraps back around to G and starts at A again. Consider the key as a palette of notes and cues to other notes and chords you can use.

Starting from any note on the scale, its triad chord is that note plus the notes 3 and 5 keys away. Its seventh chord is its triad plus the note one down from it at the top. Its ninth chord is its seventh plus the note immediately above your base note.

So that gives you G (skip A) B (skip C) D for the G triad, or G (skip A) B (skip C) D (down one from G) F# for its major. As it's been pointed out earlier, every major scale will yield the same pattern of chords from its respective notes: in your example G, you get G major, A minor, B minor, C major, D major, E minor and F# diminished triads respectively, and G major seventh, A minor seventh, B minor seventh, C major seventh, D seventh, E minor seventh and F# half-diminished seventh extended chords. I won't go into ninths, you can work out the patterns yourself if you're bored or curious.

So that's strictly the diatonic chords, the ones made up of the notes in the scale. That's the easy bit.

You can bend the scale in many different ways for interesting effect though; one of these is called a secondary dominant, and this is where a seventh chord from a completely different scale is used to lead into one of the chords from your base scale. Often the chord led into is a minor chord. It's called a secondary dominant because it's based on the fifth note of the chord you lead into.

For instance, if you want to lead into the chord A minor, you take the fifth note in the scale A minor: E. Then you work out its seventh form, E - G# - B - D. Play that, then play A minor. The third (G#) of E7 leads into the root (A) of A. Play G E7 and A and tell me it doesn't sound at least a bit interesting.

Other resources for interesting chords include parallel and related keys. The parallel minor key of G is G minor, and that gives you G minor, A diminished, Bb major, C minor, D minor, Eb major and F major to play with judiciously. Related keys of G (related based off chords in the normal scale) include A minor/C major (same notes) giving you another reason to use F major, and B minor/D major (same notes again) giving you A major and C# diminished. E minor has the same notes as G major and i suppose if you want to use a diminished scale you're free to use some variant of F# diminished though that's getting a bit tricksy.

Of course, not all the chords take ultimate priority of importance, and some are best used sparingly for effect instead of being given pivotal roles, but they're all there.

For purists: read minor as "natural minor".

[Toxikator]

You made some odd typos, I think (referring to the 7th chord as a "major", etc.) but that's just technicalities.

That's a nice primer on the secondary dominant; to put it another way, a secondary dominant is like a modulation for 1 chord only. that CHORD breaks key, acting as the dominant for some other scale. It then resolves, and, whaddya know? that chord is back in the original scale.

It's typically useful if the secondary dominant bears a strong connection to the original chord progression.

Consider the (very) common progression I-ii-V-I.

By making our "ii" into a "II", we make it DF#A, which happens to be the V chord of G... lucky us, G is also the V chord of C, so our progression goes from I-ii-V-I to I-V/V-V-I with a single accidental.

[DubGusset]

Thanks guys for the great insight. I appreciate the effort you've taken and will save this thread for further study.

Carey

[siriusbliss]

adding the 4th note in the chord scale leads to this:
Maj7 / min7 / min7 / Maj7 / 7th / min7 / 1/2dim / Maj7

Later on you can get into variations on 9ths, 11ths, 13ths, etc.

Pretty scary for only 12 notes!

Greg

[Topiness]

Apologies in advance if this is obvious:

Bear in mind that much (most?) music doesn't strictly stay in one key at all - that is, it uses accidentals (notes from outside the key) or modulation (changing to a different key for a while).

Some music doesn't even have a key identifiable by a root note, while other music does center around a root note but doesn't stick to the notes of a particular scale.

None of this is directly relevant to your question, and was touched on by k-bird - but you might find analysing existing tunes confusing if you expect them to be in a key.