What software configuration or VST do you recommend for taking a realtime audio feed and "tune" it to a particular frequency (note)?
Antares invented the Auto-Tune, which is I think what you are asking for. They do a plug-in for Evo, but generally people use the full application.
It can gently or aggressively pitch shift an input note to the closest "correct" note.
This Wikipedia article gives some background, and some example audio clips.