There might be more to it but from what I can work out this
riff is simply repeated through the whole of the song:
-/-----------------------------------------------------------------|-/-----------------------------------------------------------------|-/-----------------------------------------------------------------|-/-----------------------------------------------------------------|-/-7-7-7-7-7-7-7-6-4-4-4-4-4-4-4-2-0-0-0-0-0-0-0-4-2-2-2-2-2-2-4-6-|-/-----------------------------------------------------------------|