Methods for Changing Key
Is there any particular method to changing keys within a song? I noticed that or read it's good to change in the 5th position, e.g. C to G, but I was listening to Bobby Megge and noticed it changed from G to A for Keys.
There are a number of ways to change key during a song or chord progression. There's no right or wrong way to do it.
However, we can identify two main types of key change.
1) Key changes that use common chords of the original key.
I - ii - iii - IV - V - vi - vii
Using any of those chords as the "pivot" chord for changing key is an example of a common chord key change.
One way, as you pointed out, is to use the V (5) chord.
So, if we had a progression in C major, we could modulate to G major (the natural V chord in a C major key) and establish it as the new tonic (the tonal centre of the progression).
So we started on the tonic of C major and used its V chord, G major, to establish a new tonic of G major.
Because G major is a common chord of C major (i.e. they are both part of the same chord scale) the key change sounds very natural and seamless.
Another example of a common chord key change is to use the IV chord as our pivot chord...
The pivot chord doesn't always have to become the tonic (I) chord either. For example...
There, the ii chord becomes the vi of the new F major key.
2) Key changes that use chords "outside" the original key.
You can have a lot of fun with these, but it takes a keen ear and a lot of practice to know which chord relationships work for key changes outside the standard diatonic scale.
A safe bet is to use the relationship between the ii and V chords to get into your chosen key.
For example, starting in the key of A major, here's one way we could get into the key of Ab major:
Amaj7 / Bm7 / E7 / Cm7 / F7 / Bbm7 / Eb7 / Abmaj7
That one, something you might hear being used in jazz, makes use of the ii and V chord relationships.
The V chord can be used as a gateway to get us into a new key, as it naturally resolves to its related tonic.
What the above example did was use the ii - V relationship to reaffirm a new key.
A good tip is to use 7th chords for these non-diatonic key changes as it helps to "soften" the key change and make it sound less abrupt or just randomly thrown in.
I'll be doing an entire series on key changes so you'll learn about all these methods in more depth.
As for the Bobby Megge example, changing from G major to A major (I presume you meant major), one example of how that could be achieved is the following...
All we did was turn that Em vi chord into an E7 V chord that naturally led to an A major tonic.
So you can also change chords from major to minor, or vice versa, as a parallel switch, to get into a new key.
Hope this has helped. As I said I'll be covering this subject in far greater depth in the near future.