Ola you are correct I have the SB live value and the only effects I've seen that it can do are reverb related.
To do harmonies you'll be laying out some bucks. Check the digitech site, they have great harmony processors for both vocals and guitar. I have the guitar processor version and no complaints (RP2000). I'd be surprised if you find economical software that will do harmonies, it think an outboard effect will be your best shot......or just multi track the harmonies!