A couple of weeks ago I posted a lesson on how to change a song to any key, by using the number system. It's a great way to change the key of a song BEFORE you start playing, but a lot of you guys asked, "What about changing keys MID-song?".
So here we go! There are actually quite a few ways to change keys. Some are very technical and theoretical -- but I'm going to show you the simplest ways, so you can start using these techniques immediately.
One Thing To Remember
Before I start -- there is one thing to remember when changing keys. It's possible to change to literally any key -- but there are easier keys to move to than others. What I mean by this is that it's a lot easier (and sounds nicer) to change to a different key if that new key is 'similar' to the one you are originally in.
For example, changing from the key of C to the key of F is quite easy, because C has no sharps or flats, while F only has one flat (Bb). Changing from the key of G to the key of D is also simple because G has only one sharp (F#) while D has two (F# & C#). So that's something to consider.
There are 3 easy ways to change from one key signature to another mid-song.
1. Just do it! (Use a sus chord)
This is the 'quick and dirty' version. We just move to the new key without a transition chord. It's the simplest way, and a lot of popular music does it, but it can be quite abrupt. Most key changes that use this technique are only shifting up one whole tone (E.g. going from C to D).
It really helps to play a sus4 chord of the NEW root note. So if we're moving from the key of G to E, we'll just play an Esus4 (which means we swap the 3rd for a 4th). That helps 'introduce' the new key signature, and then we're off.
2. Using chromaticism
This is a fancy word for moving up the keyboard by half-steps until we get to the new key. We are 'stepping up' the keyboard to reach that new key. It helps create a break between the old and new so our ears can reset.
For example, if we're moving from G to A, we can use the G# note to step up to the new key. You don't even have to play a G# chord - you can just play the note, or play it as an octave, or even just a 5th (with C#).
3. Using common chords
This is, in my opinion, the best way to change keys, but it is also more difficult than the previous two. That's because it requires you to know enough theory to know what chords are in the key you are currently in -- AND the key you are moving to.
But it's definitely the smoothest and nicest transition of the three. To do it, you need to identify the common chords. Those are the chords that exist in BOTH the original and new keys.
Let's say we are in the key of D. The key of D has the following chords:
D, Em, F#m, G, A, Bm, C#dim
Now, we want to change to a new key smoothly. So we should look for another key that also has some of these chords. There are a couple of options, but the key of G works really well because it has several common chords.
The key of G has the following chords:
G, Am, Bm, C, D, Em, F#dim
So you can see the common chords are G, Bm, D & Em. That's a lot! To change to the new key we can just sit on one of those chords for an extra bar and then move into the new key.
Changing keys mid-song is a skill, and just like any other skill, it takes practice. If you think you're going to be in a setting where you will need to change keys mid-song (like at church or a band) then make sure you practice beforehand so you know EXACTLY how you are going to do it.
Just as changing keys well can really elevate a song, changing them poorly can be very jarring and offputting.
So practice and as always,