In Auto-Tune, Retune Speed refers to how quickly the plugin adjusts the pitch of an incoming note to correct it. So, naturally, the faster the Retune Speed, the more inhuman and apparent the effect. To start with, set your Retune Speed to 0 (in Auto-Tune Pro/Artist/EFX+), or to Fast (in Auto-Tune Access).
What is retune speed?
Retune Speed controls how rapidly the pitch correction is applied to the incoming sound. The units are milliseconds. ... Larger values let through more vibrato and other interpretative pitch gestures but also slow down how rapidly pitch corrections are made.
What is the best retune speed?
A Retune Speed around 25 tends to work quite well for most melodic vocals if a natural sound is what you're looking for. Some additional settings will need to be adjusted to complete the natural effect, but we'll take a look at those settings in a moment.