remastering ubuntu

[n@ughty]

hi guys
last few days, i am trying to remastering ubuntu, using remastersys
and success, but the problem is ubuntu default groups are
"adm dialout cdrom plugdev lpadmin admin sambashare"

i want to add one more group "audio".

how to change ubuntu default groups to
"adm dialout cdrom audio plugdev lpadmin admin sambashare"

thanks