Tokøta from Mastering.com walks through Logic Pro 11's Bass Player, a Session Player that reads your chords and drums to generate a full bass part on the fly.
You can lock it to a genre like Retro Rock or Indie Disco, then shape the playing with groove options (root notes only versus melodic movement), octave range, and lowest-note settings for emulating a five string bass.
Detail controls cover dead notes, slides, pickup hits, and dynamic mutes, plus a line route setting that keeps interval changes closer together for a more realistic human feel.
Swing, fill amount, phrasing length, and tempo feel (halftime, double time, or manual) round out the shaping tools.