I think I promised this to everyone last February. So here you go.
Tune down a half step. All the chords here written as though they were in standard tuning, but will sound a half step lower. I'm just writing it like this in order to make the chord shapes easier to figure out (i.e. C# is written as a D, because it's played like a regular first position D chord, though it sounds a half-step lower as a C#)
okay.
the progression for basically the entire song is:
|G---|F#m---|Em-F#m-|D---|
and the middle bit with all the ahhh's just goes back and forth between the D and Em.
And that is Sweetheart. Sorry it took so long. It's ridiculously simple.
If you aren't a fan of tuning down a half step you can Capo IV and play the chords relative to that (remember to shift the ones listed above down a half-step, though).
Thanks Tom!
This song and many others are located at the official unofficial My Morning Jacket guitar tabs and chords site:
http://mmjtabs.50megs.com/