This is mostly based on the tablature at http://tabs.ultimate-guitar.com/d/
don_mclean/empty_chairs_tab.htm - I'm extrapolating chords from the notes played 
there, and simplifying a bit when it seems appropriate. You could probably get 
away with simplifying more, though in the original the guitar is of course very 
much picking out a full melody.

G                                Asus2          Am
I feel the trembling tingle of a sleepless night
C                D7               G
Creep through my fingers and the moon is bright
G        Gmaj7 G6                       Asus2        Am
Beams of blue come flickering through my window pane
C                     D7             G
Like gypsy moths that dance around a candle flame 

      G      Asus2 Am
And I wonder if you know
     Cadd9   D7   G
That I never understood
     Em           Am7
That although you said you'd go
C               D7                G Gmaj7 G6 Am7 Asus4
Until you did I never thought you would 

G                                   Asus2          Am
Moonlight used to bathe the contours of your face
C                        D7              G        
While chestnut hair fell all around the pillow case
G        Gmaj7             G6          Am          Asus2 Am
And the fragrance of your flowers rest beneath my head
  C           D7                  G
A sympathy bouquet left with the love that's dead 

G                  Asus2  Am
And I wonder if you know
Cadd9  D7          G
That I never understood
       Em                    Am7
That although you said you'd go
C               D7                G    Gmaj7 G6
Until you did I never thought you would

Asus4             Em                  G   Am7
Never thought the words you said were true
D6    G           D6        C        Am7 Am C
Never thought you said just what you meant
Dsus2  D              G         Gmaj7 G6 Am7
Never knew how much I needed you
       D            C        D6      Am   D6
Never thought you'd leave, until you went 
G                                   Asus2    Am
Morning comes and morning goes with no regret
C                      D7         G
And evening brings the memories I can't forget
G      Gmaj7     G6        Am        Asus2
Empty rooms that echo as I climb the stairs
C                      D7                G
And empty clothes that drape and fall on empty chairs 

G                  Asus2  Am
And I wonder if you know
Cadd9  D7          G
That I never understood
       Em                   Am7
That although you said you'd go
C               D7    G    Gmaj7 G6
Until you did I never thought you would

Am7 Asus4 D7 E7 C D C D C D G