I think "hmm how to make a skrillex growl bass." Maybe make two pitchbasses hook them each up to a tube and bitcrusher.. Then make the notes the same on each but change velocities.. Crossfader? Left to right? No no, thats not it.. Right to left..Yeah yeah thats a growl bass! Now go home and try it out. Fix any imperfections. Change the waveforms a bit to add variation. Change notes to chords.