Jack Dawkins wrote:If the reason for the raised 7th is to alter the quality of the chord on the dominant, do we still expect to find it in other chords?
Only if they have a Dominant *function*.
If we are still in Am for example, do we expect to find an augmented C chord?
Not typically actually. You may find them but they are actually pretty rare. Usually in that case, the G# would be a melodic move, and not a harmonic one (that's why the concept of Melodic Minor and Harmonic Minor exist).
I think I know the answer to this, because I have played a few pieces in minor keys and I don't think I've come across any augmented chords
Yeah you probably won't. Most times Augmented chords are an alteration of either the Tonic or the Dominant chord. In fact, a strong case can be made that an altered Tonic is in many cases acting like an Altered Secondary Dominant. So instead of V-I, we'd get V+ to I. And instead of V/IV - IV, we'd get V+/IV to IV (in fact, it kind of needs the alteration to be considered a secondary chord).
The purpose of the G# is to lead to A, so putting it on III in minor would make it resolve back to i, but as it already has two notes in common it's not a very strong resolution and just sounds like the one note moving up - and again that points to more of a Melodic move than a Harmonic one.
Would we expect to find G# dim then, in Am, or does the logic behind the sharp only apply if we are talking about a chord of E? That would seem to point in favour of the E7 analysis. I tried tuning my 4th string up to E and adding that to the chord, and although this did sound fuller, to my ears it didn't change the harmony.
Yes, and that gives viio a Dominant *function*.
So V and viio (and V7 and viio7) are the *default* state of those chords in Minor Keys.
A "minor dominant" (minor v) and a plain VII (bVII) are used not to point towards the Tonic, but to another chord/Key center.
So basically, i7 is not changed to a mM7, and III is rarely changed to III+, but V and viio are *commonly* (exclusively when the composer wants dominant function) made into those chords - they use the raised 7 scale degree where i7 and III use the standard, natural scale degree.
If you encounter a raised 7 in those latter two chords, it's more likely not a *functional* appearance, but a melodic element that doesn't affect the function of the chord itself.