Watch the Mountain Bossa online guitar lesson by Fareed Haque from 1-2-3 Bossa Nova
This is another good example of of chords that serve double duty. Am6 goes to Abdim7 to Gm7. Abdim7 in this case can be re-thought of as G#dim7, or E7b9 with G#, the 3rd, in the bass. This makes sense since E7 is the V of am, so you get a i-V progression. But, one can also call the Abdim7 an G7b9 with b9 in bass. And this also makes sense because Am6 goes to G7b9 then to Gmin7, C7 and F6/9: a iii-II7-iim7-V-I. Someone go get me that aspirin, quick!