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I've been playing guitar for about 5 years... I've been slowly trying to teach myself some of the THEORY behind music..

I've just always had trouble really understanding.. When I hear a song, and attempt to start to learn it; For example, with..

Rush - Closer to The Heart

I see from research.. it's in the key of A, or so I'm told. I'm struggling to understand why. A/G/D progression-- but I see A/D fall into that key, but G does not. I can't seem to really find a key that this song fits into, at least when I lay all the chords out. The progression changes to D/G/C/A during the solo also.. again I cannot seem to understand how a key is determined from these chords. (Strictly not this song, I'm just using it as an example. Is it common to swap chords between keys??)

I've known this song for years, and I just wanted to really understand the theory behind it... to apply it to other things also.

My theory knowledge is very basic at best, so maybe I'm just not understanding something :)

Thanks for any help/insight!! :)

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The first chord sequence is similar to Sweet Home Alabama, which is also difficult to state the key. If the last chord is deemed to tell the 'key', even Lynyrd Skynyrd couldn't decide, finishing in two distinctly different ways on different recordings. –  Tim Aug 1 at 7:10

3 Answers 3

up vote 7 down vote accepted

Okay, so there's a concept missing from this question which is the tonal center. That's just a fancy way of saying the root note, the note which all others gravitate to and resolve to, which would be A in the example of the chords you gave. Key is a bit more specific, and it is usually used to mean not only the tonal center but also the scale used to construct the song.

As you note, the key "A" doesn't seem to contain all of the possible notes/chords found in this song. That's fine. We can write a song in a particular key, but then add notes and chords not found in the key.

I think what you need to know right now is that it's OK to put chords and notes in a song that are not in the key. In fact, if you don't, some people might think it sounds a little bit boring.

I think it's helpful to start analyzing the chords and giving them a roman numeral function. This will help you identify stuff that's out of the key of A major, and how that works. (Just one note outside of the key is not always such a big deal, but when a whole chord leaves the key it tends to be more noticeable).

We do this by writing a roman numeral for the pitch. A is roman numeral I, G is roman numeral bVII and D is roman numeral IV. We can also indicate the type of chord this way. But they are already major chords, so no more information is needed:

A G D I bVII VI

Now we can see the the song is "in A" but pivots off of the bVII chord.

If you want to analyze it further, you can look at the scales which the chords come from. You can say that the bVII chord comes from A mixolydian. In A major the notes are:

A B C# D E F# G# A and vii chord is G# B D, which is G#dim, a fairly uncommon chord.

In A mixolydian the notes are A B C# D E F# G A and the VII chord is G B D, a regular major chord.

You can find a bVII chord in some other scales as well, but it's most often associated with the mixolydian mode.

Now, if you decide you feel that the song isn't really concerned with A major at all, but is actually written from A mixolydian, you might even say that the "key" of the song is "A mixolydian", not "A major". By the time you come to this realization, the difference doesn't really matter much. You can think about it either way, whichever suits you and makes understanding the song more convenient.

There's still much more we could say on the subject, but hopefully that answers the question.

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Hey.. Thank you very much for the insight!! I will look further into this!!! It was very helpful. :) –  Kyle Aug 1 at 2:28
    
+1 for a great and clear answer. Indeed people tend to forget there are more scales than major and natural minor; myself included... :-) Sometime ago I wrote a small AABA piece in which the A was in Phrygian and the bridge was in Dorian and before I realised that it was a couple of days fighting the score... :-D –  Fabricio Aug 1 at 6:10
    
@Grey - A Mixolydian contains 2 # - F# and C#.This would technically be the same notes as D maj. As you state - does it matter ?! –  Tim Aug 1 at 7:14
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@Tim well, of course it can't be D major if the tonic center is A. That matters. Even then, though, if it helps a learner understand the structures they're encountering, all for it. But the choice between writing it in A major vs A mixolydian is a bit more flexible. –  Grey Aug 1 at 7:27
    
@Grey. Interesting. How would you write the 'key signature' at the beginning ? I wonder if 2# would do, but that could also signify B minor. A reader would then probably look to the last chord for a clue as to what key it's actually in. Or would they ? –  Tim Aug 1 at 7:58

Here's a simpler approach because I'm a simple guy who has to figure this stuff out on the bandstand.

In pop music, I look for I-IV-V progressions which tend to identify the key of most pop songs. The A G D progression looks like a V-IV-I progression in the key of D. But the tune seems to indicate that it's in some mode of A. So to figure out the mode I count through the modes of D until I reach A

D - Ionian
E - Dorian
F# - Phrygian
G - Lydian A - Mixolydian

So my analysis would say that the key is A Mixolydian which is A major with a flat 7.

"Simpler?" you say, "That's pretty complicated!"

I remember the modes with the following mnemonic:

I Don't Phone Lydia Much After Lockup

which translates to

Ionian Dorian Phrygian Lydian Mixolydian Aeolian Locrian

which translates to a given key starting on the note:

1 2 3 4 5 6 7

The scale of D is

D E F# G A B C#

The fifth note is A, the fifth mode is Mixolydian.

A little memorization and you can figure this stuff out fast in the future.

I like the other answer, too, but it's a little too rich for me when I'm trying to figure out something in performance with a just a guitar in my hands. :-)

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That mnemonic is a nice counterpart to "Every Acid Dealer Gets Busted Eventually". –  luser droog Aug 1 at 18:04

The G chord in an A G D progression is the subtonic chord. It is a major triad built on the lowered 7th scale degree of the key. Technically it is considered a borrowed chord since the G major triad can be built from the notes of A natural minor. As mentioned above, many rock and pop songs use this progression: Hey Jude, Don't Stop Thinking About Tomorrow and Sweet Home Alabama are just a few.

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