Well, many workstations have arpeggiators that play patterns along with whatever chords you are playing. I'd expect you'd have to program the bass line patterns yourself though, as most workstations are not thinkging about jazz musicians. The Yamaha Motifs have a very nice arpeggiator. So does the Korg Karma. If you like programming your own arpeggios I'm sure these synthes could do what you want. Most of the built in factory arpeggios are probably geared to the techno/hiphop genres.