We are going to modulate from the key of C to G using what is referred to as a pivot chord. This pivot chord will be a chord that is common to both keys and so will make the transition smooth and seem natural. So let's have a look at the key of G..
I ii iii IV V vi vii Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7b5
Looking at G we can identify that Am7 is common to both keys and so we will use this as our pivot chord for the modulation. Did you read Chord Chemistry Part 1? If not I suggest a quick look as it covers cadences which we will need to use next to complete the modulation. Lets see what we've got so far.. Cmaj7 -> Am7 -> Gmaj7 Still doesn't sound like much of a key change does it? If you start playing in your new key of G it still feels like it was a very weak transition. So we will make use of our knowledge of cadences to enhance this key change and really solidify our new key. What is the strongest cadence? An authentic (also called perfect) cadence. Which we of course know is a V - I chord change. Hopefully. So lets make use of this in our modulation, we want to establish the new key as G so that will be our I, lets grab the V chord of G and wedge it into our previous chord progression in front of the G, we now have.. Cmaj7 -> Am7 -> D7 -> Gmaj7 Now when you start playing in your new key of G you will find it has been established much better an will feel more natural. Extra ----- This is a simple key modulation because both these keys (C and G) are very closely related. There's only a difference of one note between them, the key of G has an F#, while C has an F. These keys are also close together in terms of the circle of 5ths. If you want to transition to a more challenging key then there are certainly other methods that an be used and the best way to learn is to study songs that have the kinds of change your'e after and see how it was accomplished by breaking the song down with theory. In this way you'll soon start to see music more fluidly and less restrictive. Why? ---- This is the important part. Everything you do in a song should have some kind of meaning, purpose or emotion behind it. Simply changing keys for the sake of it will be much less successful then changing key to emphasize a musical idea. I will demonstrate this if anyone is interested, and we will have a look at what I like to call the "kicking it up a notch" key change. Sorry for the long delay but I have some free time now and will be happy to share what I've learned over the years with the community here. So drop me some comments and I'll see what I can whip up for you. Mark Jones
I ii iii IV V vi vii Gmaj7 Am7 Bm7 Cmaj7 D7 Em7 Fm7b5