intro: E|-------10------------10------10-------------| B|-10-13----13---10-13----13-------13-12---12-| G|--------------------------------------------| X D|--------------------------------------------| A|--------------------------------------------| E|--------------------------------------------| E|-------------------------------------------------------------------| B|---------------10----9----------------13----12-----10-10-----10-10-| G|-9-10-12-10-------------9-10-12-10---------------------------------| D|-------------------------------------------------------------------| A|-------------------------------------------------------------------| E|-------------------------------------------------------------------|