Modulations - warning, big chunk of theory in here.
I'm going to take a look at a couple of different keys, and there relationships to other keys in order to begin explaining how to modulated, and have it sound good..
Here's my Key/scale - and its closest relatives.
G major - G A B C D E F#
dominant (or 5th degree of G) - D major - D E F# G A B C#
relative minor (or 6th degree of G) - E minor - E F# G A B C D#
In both instances there is only a single note difference between the relative scales -
For the dominant key, its the C#. For the relative minor its the D# - also note that in both instances this is the 7th degree of their respective scales.
Now in order to modulate, and have your listeners realise you've done so you must 'sound' the difference between the scales, or in other words if I'm in G and notate/play a C# then I'll sound as if I've moved to D major, but if I just start thinking in D major, my listeners would not pick it up until I use the C#.
Modulating by use of the secondary dominant chord.
I pointed out that the difference between the scales occurs on the 7th degree of the new scale - which sounds as the 3rd of a V chord, as below..
In D Major - D E F# G A B C# D E F# G A
This chord, A Major, is the dominant chord of the key D major. - When our starting key is G major, we would call this the secondary dominant for the V chord of G major (I'm sure I'm confusing people now..)
Here's a break down of all the possible secondary dominants closely relating to my original key, G major..
G A B C D E F# - now the chords from G, and their secondary dominants
G major - D major (this is not a secondary, its just the dominant.)
A minor - E major
B minor - F# major
C major - G major
D major - A major - the one I used in my minuet!!
E minor - B major - here's the relative minor
F# half dim - lets not worry about this one yet, its a little more complex.
_______________
more subtle progression -
COMMON CHORD ---> SECONDARY DOMINANT ---> TONIC IN NEW KEY.
again I'll list all the chords from G major -
G major
A minor
B minor
C major
D major
E minor
F# half dim.
Now - all the chords from my dominant key, D major
D major
E minor
F# minor
G major
A major
B minor
C# half dim
...Look closely - D major, E minor, G major and B minor chords are all common to both keys!
Why does that matter - well if i'm in G, i can seamlessly transition to any of these chords without creating any sudden unexpected changes in harmony - and they also all run into other chords in D major seamlessly because they fit in BOTH keys. So thats the common chord.
Why the secondary dominant? dominant chords naturally lead to their associated tonic chord, so the progression of common chord, to secondary dominant, to new tonic works, and gets you completely into the new key without any hiccups.
Some ways of doing this will still sound better to you than others, but I hope I've given a bit of a start as to understanding how the keys relate and how to create a seamless changing of key.
No doubt I've also sparked a million and 1 questions for some, so fire away.
AJ
Topic: Composition