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How do I know Which Key?

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(@geoff-h)
Eminent Member
Joined: 17 years ago
Posts: 28
Topic starter  

I have been teaching myself acoustic with the help of guitar noise (thank you all) for a while, and was hoping somebody could explain the following:
1 - When someone says "play it in the key of C" what do they mean?
2 - When I am strumming a song on acoustic, and I am using open chords playing G, D and C, what key am i playing in?
3 - How do I work it out?
4 - If I place my capo on fret 2, and repeat the same chords, again what key am I playing in?

Sorry for the 'dumb' questions and thank you in anticipation.

Geoff


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

I have been teaching myself acoustic with the help of guitar noise (thank you all) for a while, and was hoping somebody could explain the following:
1 - When someone says "play it in the key of C" what do they mean?
2 - When I am strumming a song on acoustic, and I am using open chords playing G, D and C, what key am i playing in?
3 - How do I work it out?
4 - If I place my capo on fret 2, and repeat the same chords, again what key am I playing in?

Sorry for the 'dumb' questions and thank you in anticipation.

Geoff

If a song is in the key of C (major), it means that most, if not all, of the notes that make up the tune and chords belong to the scale of C major. In addition, it means that the songwriter has arranged the notes and chords in such a way that the note C and the chord C major can be felt as the 'key' or 'home' note and chord that we always expect to return to, especially at the ends of verses or choruses. The majority of songs end on the key chord as that's the only one that gives a feeling of finality. Ending on any other chord produces something of an unfinished feeling - (which can also be a good musical effect).

Almost all simple songs end on the key (aka tonic) chord and key note. For example, think of "Happy Birthday". Even when just sung with no chord accompaniment, the final ..."TO YOU" has that unmistakeable feeling of having arrived home. It signals the end of singing and the resumption of drinking :D

If the chords of a song are C G & D, it's probably in the key of G major, as G major is the only major scale whose notes can be combined to produce all three of those chords. But it could also be in the key of D major, with the chord C major being an outside chord borrowed from another scale to give a particular effect.
The acid test is "whichever major or minor chord sounds like the home chord, then that's the key" regardless of any foreign and exotic chords that the song may contain.

If you're playing a song in the key of C major, and then capo on fret 2 while playing the same shapes (2 frets higher), then you're now in the key of D major. Each fret shifts the key by one semitone or half step (C> C# > D)


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

Here's a useful table of the notes in the different keys:
Major Relative Key I ii iii IV V vi vii°
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
----------------------------------------------------------------

The primary chords in each major key are the I (1), the IV (4) and the V (5). In C major they are C,F and G, in G major they are G,C and D and so forth.

--
Helgi Briem
hbriem AT gmail DOT com


   
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(@geoff-h)
Eminent Member
Joined: 17 years ago
Posts: 28
Topic starter  

Many thanks Hbriem and Fretsource,

That is very useful. The table is a very useful addition to my 'notebook', and the explanation clarifies a few things I had wondered.

So if I were to take Johnny B Goode - I have seen this written 2 ways (there are probably loads more), the verse, being
G...............
G..............
C................
G.............. then
D7.............C
....G..........D7
chorus
(Go, Go)G.....................C...............G
......D7 C................G D7

Example 2
A
A
D
A
E.............D
...A..........E
A.......................D.............A
.......E D..............A..E

Using you I, IV, V explanation the first example uses G, C D(7), your table indicates that is in the key of G Major - correct?
The second example uses A, D and E which your table indicates is in the key of A Major.

I have again looked at the table and had a go at it in the major keys of C, G, D and A, but I struggle with the B chord and the rest I will have to practise with barre chords.

A bit more theory 'in the can'. Thank you again.

Geoff


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

Actually, that song is a great example of verses and choruses ending on chord V7 (the dominant 7th), rather than chord I (the tonic or key chord). The V7 chord, especially in that position, defines the key just as well as chord I. Unlike the I chord where you feel it has arrived home, the V7 at the end feels unmistakably "away from home and demanding to get there soon" (to start the next verse in this case).
V7 points strongly to the key because it's dissonant and its most natural resolution is to chord I, which is always a perfect 4th higher (or perfect 5th lower - same thing). So in the key of G, the chord D7 wants to resolve to the key chord G (or G minor if it's in a minor key), In the key of D, A7 resolves to the key chord D, etc.
Eventually the song must either fade out or finally end on chord I, or you'll never hear the end of it as the V7 chord always drives it on. That's it's job.


   
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(@geoff-h)
Eminent Member
Joined: 17 years ago
Posts: 28
Topic starter  

Thank you again for the explanation. Amazing what you can learn from a 'simple' arrangement. Now for a few of the solos!

Cheers


   
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(@wes-inman)
Illustrious Member
Joined: 20 years ago
Posts: 5582
 

Geoff

As you can see in your example of Johnny B Goode, you can play any song in any key. The intervals are going to be the same (start with Root chord, go to IV, back to Root, then V chord, IV chord, Root, V7...)

Usually, the main reason to change keys is to fit a singer's voice. Often you might find it difficult to sing a song in a particular key like C for example, but find it very easy to sing the notes in D. So, it's good to know how to transpose to another key.

Another reason is to make it easier to play. Some keys are very easy on guitar like C, D, G, A and E, whereas some keys are more difficult like B as you mentioned. So, just play the song in an easier key. :D

Sometimes you have to play in another key to play along with other instruments. You go out to an Open Mic and a Blues harp player comes up, only has one harp. You are going to have to play in a specific key for him to play along.

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis


   
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(@bmancv-60)
Estimable Member
Joined: 16 years ago
Posts: 135
 

I have been teaching myself acoustic with the help of guitar noise (thank you all) for a while, and was hoping somebody could explain the following:
1 - When someone says "play it in the key of C" what do they mean?
2 - When I am strumming a song on acoustic, and I am using open chords playing G, D and C, what key am i playing in?
3 - How do I work it out?
4 - If I place my capo on fret 2, and repeat the same chords, again what key am I playing in?

Sorry for the 'dumb' questions and thank you in anticipation.

Geoff

For question 3 - One of the things I've learned recently that seems to hold true is follow the bass player; they tend to anchor the song.

"...I don't know - but whasomever I do, its gots ta be FUNKY!"


   
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(@geoff-h)
Eminent Member
Joined: 17 years ago
Posts: 28
Topic starter  

Wes - thank you. that is what I was after, why do we want to play it in another key? I guessed that I might like to choose a key without a difficult chord in it, for simplicity. Playing with others brings the other reason in to play, not done that before last night - see my jam post.

Cheers


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

There are several reasons why you might want to play a song in a different key.

1 - You might want to play it with the easiest chord forms. The easiest keys from that viewpoint are:
G/Em : G, C, D or D7, Am, Em are all easy chords, Bm fairly easy.
C/Am : C, G or G7, Am, Em are easy chords, F (at least the cheat version) and Dm fairly easy.
D : D,G, A or A7 and Em are easy, Bm fairly easy.
A : A, D and E or E7 are easy chords.

2 - You might want to play it with particular chord forms for voicing reasons or for the ease of incorporating particular notes (for example open ones). This gets somewhat more complicated and specialised.

3 - Most commonly, you might want to either accomodate the singer or a particular instrument. The singer might have trouble reaching the high notes in D, but might do fine in A. Many instruments are easy to play in some keys and hard in others. Many brass instruments play best in Bb or Eb. Harmonicas only play in one key.

--
Helgi Briem
hbriem AT gmail DOT com


   
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