Hello. There is already another bass tab of Horror show:
http://tabs.ultimate-guitar.com/t/the_birthday_massacre/horror_show_btab.htm

I listened the song for many times. I tried to play Horror show using that tab.
I watched video of TBM performing the song (bass player is visible during most part of video):
http://www.youtube.com/watch?v=tYVnM9oOQ8o

And I think that bass line in this song simplier then in tab I linked above (just my opinion).




Horror show - The birthday massacre

Tabbed By: rogerpirks
Tuning: DADG

riff 1
G|--------------------------------------------------------------------------|
D|----2222--------------2222------------------------------------------------|
A|0000----33333333--0000----33333333----------------------------------------|
D|------------------------------------7777555500000000--7777555500000000----|

riff 2
G|---------------------------------|
D|---------------------------------|
A|33333333--------22222222---------|
D|--------22222222--------00000000-|


Sequence of riffs

Intro: 1
Verse: 1
Chorus: 2222
Pre-verse: 1
Verse: 1
Chorus: 2222

from 2:24 to 2:56 there is riff 2 being played on a synth four times, and the bass is silent

Chorus: 2222
Outro: 11