On the same block, but down the street a few houses, lives your cousin and her family. At any given moment, who are the most likely people to be in your house? Obama? Payton Manning? Rush? Barry Bonds? I don t think so! It s possible, of course, but not too likely. If I had to guess, I would say it would be either you, your spouse, or your child. It might be your cousin down the street there s a much better chance of that than, say, Hillary or George - but my best odds would be to guess that the family members would be there. It s the same way with chords. In any given key, there are 3 family members that are residents of that key - the I chord, the IV chord, and the V chord. They are far and away the most likely chords to occur in any given key. What chord comes next? So how could I tell whether it should be F or G? If the melody is a B , then the chord is probably a G chord. Why? Because B is in the G chord, but is not in the F chord. If the melody is a A , than I would guess that the chord is F. Why? Because A is in the F chord, but is not in the G chord. Does that mean that there are always just 3 chords in a song? No, but the...