Watch the One Beat online guitar lesson by Brad Carlton from Chord Studies: Jazz Turnarounds Vol. 3

Here again we'll be applying that b5 substitution principle. We start with the same Fmaj7 chord and then we move up to an Am7. Why can we do this? Because it's a 3rd away from where you were, and any two chords that are a third apart will have common tones. For example, Fmaj7 is F-A-C-E and Am7 is A-C-E-G, so you can see that they share three common tones.