Mighty River
The intro is Aadd9 - Em - Dsus2 played as a lick. It's not a G. Listen to the bass. G and Em are relative major and minor, both in the A mixolydian mode of the song, so it's easy to confuse them. But it's Em.
Aadd9 - Em - Dsus2
-0-------------7---------------------------------
-0-------------8-------5------5--------5--------
-6-------------9----------7-----7---------7------
-7-------------9------------7------7----------7--
-0-------------7----------------------------------
---------------------------------------------------
Verse is all open chords, first position Em-G-D-A Em-G-D-D
Then there's a descending line here and there:
Em - D - A - G - A | Em - D- A - G - D
---------------------------0------------------------------2--------------
--8----7------------------0---------8---7---------------3-------------------
--9----7-----9------7----6---------9---7---6--4-------2-------------------------
--------------11-----9---7------------------7---5------0--------------------
---------------------------0-----------------------------------------
--------------------------------------------------------------------
Hope that helps
Seth
http://www.gratefulguitarlessons.com