How do you transition from one key to another?
The smoothest way to modulate from one key to another is to use a pivot chord. A pivot chord is a chord that both keys share in common. For example C major and G major share four chords in common: C, Em, G, and Am. Any one of these chords can be used to transition smoothly from C major to G major.
What is a transition chord?
It's usually between the verse and chorus that a key change will happen if at all. ... Everything is given in either the key of C major or A minor, but are transposable to any starting key you wish. For each key change, you are given an example of what a good transition chord might be – the chord that bridges the two keys.