hi i think this is one of the most experimental song of all music
you really have to made an effort to sing with the guitar chords because the guitar is
of tune with the viola and the voice (the viola plays in the first part G#and the voice
to that  while the guitar is playing this chords:

C(put the fingers as D cause the guitar is two half steps down every string)

G(sus 4) (fingers like A (sus 4))

Eb 2 times(fingers like F but without bar cause you have to play only  4 strings,the
notes)

for  C you have to play 4th-3th-2nd string (all together )

for G(sus 4) you have to play 5th-4th-3rd string(also the 2nd if you want to play sus4 )
together

for Eb you have to play also the little melody(i think in the original the guitar play
these notes without the chord support but if you play alone with an acoustic guitar  its
to play with the chord support in this way the sound seems more complete): Eb Eb Eb D Eb 
C (to do with the 1st and 2nd  string and the chord support with the 3rd and 4th string)

 other time you  do this passage(instead of the 2nd Eb chord):3-3-3-2 simultaneously on
3rd and the 4th string and playing only these 2 strings (the 3 is when the guitar is for
only time in the song in perfect tune with the viola but when you listen the song this 
the strangest moment)

the rithm is like this: C C C C G
G G Eb Eb Eb D Eb 
C (x32010@1) Chords of the chorus (this time the viola seems a little more in tune,but not so much,
the guitar but again the voice is singing in a different key!!!):
Eb (fingers like F without bar as previous) -
 G# (fingers like Bb on the 1st fret)
 - Bb (fingers as C)
 then
 Eb (2 times and also with 2-3-2 on the 3rd string)-G# (fingers as .....)- Bb(....)-Eb
times as before) -G#(..)-
Bb(..)-Eb (1 time) -
  C (fingers as D on the 5fret and play all the strings except the the bass one (the 6th))

if you sing and it seems to you a "normal" song then you are just following the guitar
with the voice

try to play the guitar and sing as in the song i think your hear will open to new
(of course very crazy ones !!!!!)