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defining the key

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(@aarrgg)
Eminent Member
Joined: 18 years ago
Posts: 32
Topic starter  

This maybe seem to be a stupid question but I can't find a good explanation that I understand.
How to define what key a song is in?
What use do I have of knowing the key?
I appreciate any answers.

"I face myself, to cross out what I've become
erase myself, and let go of what I've done"
- Linkin Park


   
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(@fretsource)
Prominent Member
Joined: 18 years ago
Posts: 973
 

Knowing the key of a song means you can predict the chords that will most likely be used in that song. For example, if you ask me to accompany you singing a song such as "Let it Be" in the key of F, then I know to expect the chords of F, Bb and C because those are the main chords belonging to that key. I'll also expect D minor and A minor might make an appearance.

The key refers to ONE NOTE that feels central to the whole song plus an accompanying set of notes, usually from either the major or minor scales that start on that note

So a song in G major generally means the note G is the main note and all the other notes will be notes of the G major scale. All the notes relate to G in such a way that it sounds complete and "at home". That's why the key note is almost always chosen as the final melody note.


   
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(@guitarteacher)
Trusted Member
Joined: 18 years ago
Posts: 46
 

Well answered by Fretsource. I would only add that the chord for which the key is named acts as a home chord in the same manner as the home note.

Knowing the key is important if you need to change the key, as well. I always think of chords in terms of function, as this allows me to put the piece into a new key more rapidly. By function, I mean thinking of F, Bb, and C (to borrow Fretsource's example) as I, IV, and V . Being able to change keys is important if you are working with vocalists or if you are arranging music for the solo guitar.

If you want to be good, practice. If you want to be great, you must constantly change the way you think.


   
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(@aarrgg)
Eminent Member
Joined: 18 years ago
Posts: 32
Topic starter  

Thanks, I think you cleared things up a litle bit but now I got even more qustions. :?
I dont' see why Bb and C is the main chords of F. Is that because they are IV and V of F?
And why are you expecting Dm and Am? Is that because they are III and IV of the F scale? (I isn't sure they are).
What defines if the notes in a song are from the minor or major scale of the key?
I don't now if these questions are even relevant or if my assumptions are correct but I appreciate all help I get.

"I face myself, to cross out what I've become
erase myself, and let go of what I've done"
- Linkin Park


   
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(@aarrgg)
Eminent Member
Joined: 18 years ago
Posts: 32
Topic starter  

Oh, sorry Guitarteacher, I didn't saw your post before I posted mine. :oops:
I apparently was correct that Bb and C is the IV and V but the rest of my questions are still unanswered.
Thanks

"I face myself, to cross out what I've become
erase myself, and let go of what I've done"
- Linkin Park


   
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(@fretsource)
Prominent Member
Joined: 18 years ago
Posts: 973
 

Exactly! Bb and C are the IV & V chords of F major. Apart from the I chord (F), those two are the most important and the most likely to occur in songs.
I'd also expect chords Dm and Am because they are the vi and iii chords, Not so common as IV and V but still very common. I probably should have mentioned chord ii (Gm) after vi (Dm) as those two are both more common than iii (Am).
So the primary triads (I, IV & V) are almost certain to dominate the song.
The secondary triads (ii, iii & vi) are very possible, so I'd be looking out for them.
chord vii is a diminished triad, and in a song as straightforward as the example I gave (Let it Be) I wouldn't be expecting it at all.

What defines whether the notes are from the minor or major scale is the songwriter. He or she decides whether to write a song in a major key or a minor key depending on the mood they want to create. Or maybe they just stumble on a lovely melodic phrase or chord progression and develop it from there. If the notes of that phrase happen to be from a minor scale, then that's how the song will be written - in a minor key - using the notes and chords of the minor scale.


   
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(@hbriem)
Honorable Member
Joined: 22 years ago
Posts: 646
 

Time to throw in some tables once again. A lot of people have found these useful:

Key Signatures (with relative minors)



Key Minor Signature 1 2 3 4 5 6 7
C major A minor C D E F G A B
G major E minor # G A B C D E F#
D major B minor ## D E F# G A B C#
A major F# minor ### A B C# D E F# G#
E major C# minor #### E F# G# A B C# D#
B major G# minor ##### B C# D# E F# G# A#
F# major D# minor ###### F# G# A# B C# D# E#
F major D minor b F G A Bb C D E
Bb major G minor bb Bb C D Eb F G A
Eb major C minor bbb Eb F G Ab Bb C D
Ab major F minor bbbb Ab Bb C Db Eb F G
Db major Bb minor bbbbb Db Eb F Gb Ab Bb C
Gb major Eb minor bbbbbb Gb Ab Bb Cb Db Eb F

Harmonising the major scale (with example in C major)
Degrees of notes C major scale notes
1 2 3 4 5 6 7 8 C D E F G A B C Chord no. Chord name
-------------------------------------------------------------------------
1 3 5 C E G I C major
2 4 6 D F A ii D minor
3 5 7 E G B iii E minor
4 6 8 F A C IV F major
5 7 9 G B D V G major
6 8 10 A C E vi A minor
7 9 11 B D F vii° B diminished

Common Chord types
Chord Notes Example in C Name
major 1 3 5 C-E-G C major
6 1 3 5 6 C-E-G-A C6
7 1 3 5 b7 C-E-G-Bb C7
maj7 1 3 5 7 C-E-G-B Cmaj7 or CM7
9 1 3 5 b7 9 C-E-G-Bb-D C9
maj9 1 3 5 7 9 C-E-G-B-D Cmaj9
11 1 3 5 b7 11 C-E-G-Bb-F C11 (rare)
C#11 1 3 5 b7 #11 C-E-G-Bb-F# C#11
add11 1 3 5 11 C-E-G-F Cadd11 (rare)
13 1 3 5 b7 13 C-E-G-Bb-A C13
add9 1 3 5 9 C-E-G-D Cadd9
sus4 1 4 5 C-F-G Csus4
sus2 1 2 5 C-D-G Csus2 (Gsus4, 1st inversion)
5 1 5 C-G C5
aug 1 3 #5 C-E-G# Caug
6/9 1 3 5 6 9 C-E-G-A-D C6/9
minor 1 b3 5 C-Eb-G Cm or c
min7 1 b3 5 b7 C-Eb-G-Bb Cm7 or c7 or c-7
minmaj7 1 b3 5 7 C-Eb-G-B Cminmaj7 (CmM7)
min9 1 b3 5 b7 9 C-Eb-G-Bb-D Cmin9
dim 1 b3 b5 C-Eb-Gb Cdim
dim7 1 b3 b5 bb7 (6) C-Eb-Gb-A Cdim7
min7b5 1 b3 b5 b7 C-Eb-Gb-Bb Cm7b5

--
Helgi Briem
hbriem AT gmail DOT com


   
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(@aarrgg)
Eminent Member
Joined: 18 years ago
Posts: 32
Topic starter  

Now I think I understand most of it.
Thanks Fretsource and Hbriem. Really appeciate your help.

"I face myself, to cross out what I've become
erase myself, and let go of what I've done"
- Linkin Park


   
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(@mimifox)
Eminent Member
Joined: 18 years ago
Posts: 13
 

I learned this by trying to understand why all the chords in the key aren't major, ie trying to build a major triad from every degree of the major scale of that key to understand why it *doesnt* work. For instance in C, try to build major triads from C, D, E, F, G, A, and B:

So the I chord would be built from C, E and G (The root, major third and pefect fifth or the C major scale). Each of these notes are in the key of C, so this chord is in the key of C (obviously). So since the relationships between the intervals in any key are the same, we know that in any key, the I chord is major.

But for the ii chord, building a major triad from the D major scale doesnt work, we get the notes D, F# and A. The F# is not in the key of C so we flatten this note to an F, which is in the key of C giving us a Dm triad: D, F and A. So the ii chord is minor.

If you continue in this manner up to the 6th degree of the major scale that the key is based upon you get this pattern:

I - Major
ii - Minor
iii - Minor
IV - Major
V - Major
vi - Minor

Now when you try building your major triad off of the 7th, you realise it's a bit of an odd one - you get the notes B, D# and F#, neither the D# nor the F# are in the key of C, so both must be flattened, giving a chord (which is now in the key of C consisting of the notes B, D and F) with a formula of 1, b3, b5: a diminished chord. So the triad build off of the 7th of any key gives a diminished.

So the triads that can be built in any key are like sooooo:

I - Major
ii - Minor
iii - Minor
IV - Major
V - Major
vi - Minor
vii - Diminished

So say you see a G# diminished chord in a song, there's a good chance it's in the key of A. Or if you see an E minor, you're probably in either
D, C or G.

Hope that helps sombody.

I don't really understand minor keys atall, so if sombody could explain how they fit into my (probably poor) understanding of keys (the stuff i just wrote *points* ), I'd be grateful :D. Thanks in advance.

Mimi


   
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(@fretsource)
Prominent Member
Joined: 18 years ago
Posts: 973
 

Chords of minor keys.

Hi Tom, you'll find answers to your question on a recent thread.
http://forums.guitarnoise.com/viewtopic.php?t=26113


   
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