Remember: Auto-Tune cannot fix a boring performance. But a free VST can fix a flat chorus. Now go make noise.
A free VST will not sound like Antares Auto-Tune Pro ($399). But you can cheat. Here is how to get professional results from a : autotune vst for adobe audition 15 free
If your goal is to fix a vocal performance without it sounding like a robot (the "Invisible" Autotune), follow these settings in the plugin: Remember: Auto-Tune cannot fix a boring performance