The bass comes in at about the middle of the song to accompany the guitar.
1:44-

Part 1                          x1|Part 2                        x4
G|3---3---3---3-------------------|3---3---3---3/6-------------3/8-|
D|--------------------------------|--------------------------------|
A|----------------4---4---4---4---|----------------4---4---4-------|
E|--------------------------------|--------------------------------|

Part 3                          x14
G|3---3---3---3-------------------|
D|--------------------------------|
A|----------------4---4---4---4---|
E|--------------------------------|

It's just this simple bassline with a couple of slides and that's all there
is to it. The chello plays a more complex tune but I haven't been able to
figure that out as it sounds completely different on a bass or guitar. Here is the whole tune:
http://www.youtube.com/watch?v=Z7LjjmSYTdQ