Instead of introduction being:
Am D Am7
Try these chords:
Am: x 0 2 2 1 0
??: x 0 4 4 3 0 in place of D, you might call it a Bm7+11
??: x 0 6 6 5 0 in place of Am7, you might call it a C#m
The low A is a drone note that continues through the intro