Watch the Leaving Home Base online guitar lesson by Matthieu Brandt from Songwriting on Guitar

Chord progressions move from a state of balance and rest to a state of tension and back again. When you've found the key you are composing in, you know which chord gives you that 'home 'feeling. The song will feel at rest when you play that chord. Other chords within the key will give you some degree of tension and a feeling that you're on the move. You have left home.
Making sure the listener knows what home is, techniques to move away to a home 'outside of home' and sets of chords that go together well is what this lesson is about. How far away you stray from home, is only a matter of which chords you chose.