The key/scale of the great highland bagpipes is A 
mixolydian, however their music is written with no 
sharps or flats.  I tabbed this out so the music reads 
correctly, but the notes won't be right - for transposition 
to other instruments, you would play A# mixolydian, 
though again, with a real highland bagpipe, it will be 
out of tune as the pipes are not only inbetween pitches 
(in comparison to concert pitch of A4 = 440 hz), but 
they are also un-even tempered.  All of the A notes are 
exact octaves of each other, but the two G's are not 
perfect octaves of each other.  The correct tuning for 
the GHB is listed below.  Also in this tab, the top line of 
the four is for the chanter, the two in the middle are for 
the tennor drones (A3), and the bottom for the bass 
drone (A2).  Also, I'm not sure what type of bagpipes 
were used in this song, but they're not GHB, and I've 
listed their tuning at the bottom.

The drums aren't actual drums, the album was written 
and recorded by two guys, but they employed an entire 
commune in helping them record, the drums in this 
song are actually a bunch of the members of the 
commune clapping, beating on rocks with sticks, and 
stomping their feet.

The distorted noise that sounds like an electric guitar is 
basically tuned normally, except that it is tuned 50 
cents higher, so that the A matches the A on the 
bagpipes, but this is basically the only chord it plays so, 
it works.

--Modern Bagpipe Tuning--
Drones:
Tennor Drones A3 = A#3 + 33 Cents
Bass Drone A2 = A#2 + 33 Cents

Chanter:
G4 = G#4 + 3 cents (+103 cents)
A4 = A#4 + 33 cents (+133 cents)
B4 = C5 + 35 cents (+135 cents)
C4 = D5 + 20 cents (+220 cents)
D4 = D#5 + 30 cents (+130 cents)
E4 = F5 + 36 cents (+136 cents)
F4 = G5 + 18 cents (+218 cents)
G5 = G#5 + 1 cents (+101 cents)
A5 = A#5 + 33 cents (+133 cents)

(One semitone = 100 cents)

Now, that is based on the GHB's of today, but the 
tuning standards have changed over the years and for 
this particular song, the tuning of the pipes is:

--This Song's Bagpipe Tuning--
Drones:
Tennor Drones G2 = G#3 (+100 cents)
Bass Drone G2 = G#2 (+100 cents)

Chanter:
G4 = 
A4 = A4 + 50 cents (+50 cents)
B4 = B4 + 50 cents (+50 cents)
C4 = C#4 + 50 cents (+150 cents)
D4 = D4 + 50 cents (+50 cents)
E4 = E4 + 50 cents (+50 cents)
F4 = 
G5 = G#5 (+100 cents)
A5 = A5 + 50 cents (+50 cents)