I don`t use with bass songs, so I cannot tell so much about that feature, but here´s a link to a thread from a member, explaining how to create a "with Bass" drum set: http://mybeatbuddy.com/forum/i…s-bb-songs-on-a-mac.4896/
There are some Kits including bass already, but as far as i understand, there are some compromises, since the BB does not use Midi off notes (atm), but by the permanent improvement, I think it is only a question of time (IMO). But as I said, I am not so sure about that thing, if you are really interested, please ask in the BB Forum...