Waves Tune Real-Time is a professional pitch correction plugin known for its low latency and ease of use in live and studio environments. While the full version typically retails for around (often on sale for ~$35), there is no permanent free version available for download .
If you are looking for completely free software, Waves offers a Free Plugin Pack waves tune realtime free download free
Allows MIDI notes to dictate exact pitch targets (Windows only). Waves Tune Real-Time is a professional pitch correction