It’s relatively commonplace to change key in the middle of a song. It happens for various reasons, but probably the reason that stands out over the others is the need to increase the song’s overall energy. In that regard, you’ll find that raising the key by a half-step (semitone) or a whole step (whole tone) will achieve the desired result.
Other reasons you might change key: to put the song in a better key for a duet partner, or simply to add variety to a song that is somewhat repetitious. Also, if you want to move from one song to the next in a performance, without any obvious break, changing key with a clever progression is the way to do it.
Whatever the reason, it needs to be done carefully. Most of my e-books deal with this interesting part of chord theory, and I’ve included some examples below that I hope you find useful. The starting key is C major, but just transpose them into any starting key of your choice:
Example 1: A Progression that Moves Up 1 Semitone:
C F G7 C Ab7 Db
Example 2: A Progression that Moves Up 1 Wholetone:
C F Em A7 D
Example 3: A Progression that Moves Up a Minor 3rd:
C Gm7 Ab Bb7 Eb
Example 4: A Progression that Moves Up a Major 3rd:
C G/B B7 E
Example 5: A Progression that Moves Up a Perfect 4th:
C Am Gm7 Csus4 C7 F
These are just two of many possibilities. Feel free to experiment. And if you really want to learn what the great songwriters out there are doing to make their songs so great, you really need to click here.
-Gary Ewer, from “The Essential Secrets of Songwriting” website:
Songwriting tips! Write Better Chords, Melodies and Hooks!.