Are you looking for a FREE alternative to Autotune? Auburn Sounds may have just the plug-in for you. The free version of their Graillon 2 provides real-time pitch correction and pitch-shifting.
The pitch shifter has two controls; the standard 'static pitch-shift can be used to move the entire audio signal up or down in pitch. A 'preserve formants' knob lets you control how much of the original spectral envelope you preserve in the pitched signal.
The pitch correction module contains five rotary controls, as well as a piano keyboard that is used to select the notes that the pitch-correction algorithm will use. Through these controls, ('Inertia', 'Smooth', 'Snap Range', 'Reference' and 'Correction Amount') you are able to create a broad range of pitch-shifted vocal effects, from robotic sounds, through to more natural, 'transparent' pitch correction.
This is a 'freemium' product, meaning that you can upgrade to the paid version (for €29) to unlock extra features such as a bit crusher and a very interesting 'pitch-tracking modulation' module. This can be used to create choruses or octaver sounds and it can supposedly even 'enrich a voice to make it more masculine'!
Even without the upgrade, there is plenty about this plug-in that makes it worth a look. It is available for both Mac and PC in VST and AU versions, at both 32-bit and 64-bit. You can download it from the Auburn Sounds website.
Audio Ear Training for Music Producers and Sound Engineers