Try taking a bass wave like 260 sine bass, MC 202 Bass or SH 101 Bass and then push it through the low pass filter with mid resonance and the filter about say 80. Go to the pitch envelope menu and try putting the envelope depth at -12. Then, put the attack time to about 20 or 30. Try doing the same with the filter envelope as well. I'm just recalling all this from my head so it might be alittle off. Anyway, just mess around with the filter settings after you've set the envelopes. Also, try to make use of the portamento for the bass slides.