Elastic Pitch is worth a try(but only the Polyphonic algorithm allows for pitch change). Serato Pitch 'n Time is excellent for this(they may have a free demo period so you can process your bass permanently because it works in AudioSuite for this). Zplane's Elastiq is another good one(but start with Elastic Pitch because you already have it). Half and whole-step changes should be fine. The more expensive options tend to maintain better sound quality with larger changes
