This is a tab for Hoppipolla by Sigur Ros. I've figured it out by myself with piano and 
with guitar.

Tuning: Standard. (In original Hoppipolla the piano has an unoriginal tuning. Use a capo 
first fret if you wish to have same pitch.)

INTRO:
E|-----------------------------------------------------------------|
B|-------1-------1-------1-------1-------1-------1-------1-------1-|
G|-----3-------3-------3-------3-------3-------3-------3-------3---|
D|-0-3-----0-3-------3-------3-------3-------3-------3-------3-----|
A|-----------------3-------3-------1-------1-------3-------3-------|
E|-----------------------------------------------------------------|

MAIN MELODY (right after intro and continues until chorus):
E|---------------------------------------------------------|
B|-------1-------3-------3-4-3-----------3-4-3-----------1-|
G|-----3-------3-------3--3----3-------3--3----3-------3---|
D|-0-3-----1-3-----1-3-----------3-1-3-----------3-1-3-----|
A|---------------------------------------------------------|
E|---------------------------------------------------------|

E|---------------------------------|
B|-------1-------3-4-3-----------1-|
G|-----3-------3--3----3-------3---|
D|---3-------3-----------3-1-3-----|
A|-3-------3-----------------------|
E|---------------------------------|

Its pretty much a steady flow exept the fast high part. You'll learn best by listening 
the song and comparing it to your playing.

Chorus (same as intro):
E|-----------------------------------------------------------------|
B|-------1-------1-------1-------1-------1-------1-------1-------1-|
G|-----3-------3-------3-------3-------3-------3-------3-------3---|
D|-0-3-----0-3-------3-------3-------3-------3-------3-------3-----|
A|-----------------3-------3-------1-------1-------3-------3-------|
E|-----------------------------------------------------------------|

Tunnel after chorus(followed by main melody again):
       E|-------------------------|
       B|-------1-------1-------1-|
       G|-----3-------3-------3---|  Main melody starts here. (x2)
       D|-0-3-----1-3-----1-3-----|
       A|-------------------------|
       E|-------------------------|
Og ég fæ blóðnasir     En ég stend alltaf upp

Timing is improtant here. Tunnel starts exatcly when he sings "blóðnasir" and main 
starts when he sings "alltaf". Again helps if you listen to the song.

After the main melody has been played twice tunnel starts again with same timing. After 
the main melody plays until the end of the song.