Stephen Calder wrote:
> Rufus wrote:
>> Paul P wrote:
>>>
>>> Stephen Calder writes :
>>>
>>>> Paul P wrote:
>>>>> Stephen Calder writes :
>>>>
>>>>>> G-B7-E7-A7-D7-G.
>>>>
>>>>> That's a circle of fourths
>>>>> (well, almost).
>>>>
>>>> Yeh, but what key is it in?
>>>
>>> If the chord progession is as written I'd say it's in G.
>>> If played with open chords on a guitar the high note
>>> goes G, F#, E, (pause), E, F#, G. Looks like a blues
>>> turnaround to me.
>>>
>>> In theory, though, I'd guess that this was the key of G
>>> modulating to the key of E by way of the B7, then
>>> modulating back to the key of G by way of the D7.
>>>
>>> There are three notes that are present in 3 out of the
>>> 5 chords : A, B, and D. There are three notes that are
>>> present in all the major scales associated with the
>>> chords : F#, B, and E. So I vote for the B to be the
>>> basis of a one note solo on this chord progression.
>>>
>>> I just read an interesting thing : taking any 5 consecutive
>>> notes from the circle of fifths produces the major pentatonic
>>> scale for the note you started on.
>>>
>>> Paul P
>>
>> That's probably why I asked what chord his progression resolves to -
>> whatever that is, that's what I'd call the key and play the solo in.
>>
>> ...so, in this case, it appears to be G, or likely G minor...to me.
>>
>
>
> I was responding to the proposition that if you know how to harmonise a
> scale, you'll always know what key you're in.
>
> That's true for simple songs, but in this progression we're changing key
> with every chord.
>
> A seventh chord always wants to resolve to the major chord a fourth away
> (B7 to E). When we switch to B7 from G we are suddenly in the key of E,
> the key of the chord that B7 wants to resolve to.
>
> From there the progression briefly moves to each of the keys A and D
> before cycling back to G.
>
> It's not always that easy to tell what key you're in from the
> progression alone, but 99 per cent of the time, if you have, say, a G7
> chord, it's a big clue that key is C.
>
> The circle of fifths will tell you what each seventh chord will resolve
> to. It resolves to the chord to the left.
>
>
> F C G D A E B Gb Db Ab Eb Bb F C G etc
>
>
>
>
> G7 resolves to C, E7 resolves to A, F7 resolves to Bb.
>
>
>
>
>
>

All those 7ths sound funny to me because as you point out they don't
resolve each other through the progression, but that's not really what I
was getting at.

I was talking about choosing a key for playing a lead - more at what
does the progression "resolve to" - i.e.; in keeping with the point
about where you start being the root of a penatatonic scale, then if the
progression starts in G and returns to G, I'd play a lead predominantly
positioned in G over it...I'd also be likely to "play the change" at the
bridge (whatever it is...), but that's only because it's my habit from
playing a lot of blues that way.

Noodling through the progression as written - G-B7-E7-A7-D7-G - I can
improvise a lead that follows those changes and still keeps my left hand
in a position that uses the blues minor pent scale -

http://guitarsphere.com/wp-content/uploads/2007/10/minor-pentatonic-scale.jpg

(which is the first scale I ever learned, and what I play the most of)
rooted in G and using notes in 1st, 2nd, and 5th positions. So the way
I'd play it, I'd call the key of this progression as G or G minor
because that's what I'd use to play a lead over it.

--
- Rufus