EFX is the cheapest version of Auto-Tune. Priced around $100 U.S., it is a standard plug-in that you can use with music editing software, such as Pro Tools, Logic, Record, Audition and Ableton. Auto-Tune EVO costs around $200 U.S. If you are unsure of which version you need, Antares, the creators of Auto-Tune, allow you to upgrade from your purchased version of EFX to a version of EVO for an upcharge that ranges between $90 and $130 U.S.
EFX and all of its components fit in a small box that takes up roughly one-fourth of your computer's screen. There is a menu for choosing the range of your singer, such as tenor or soprano, one for choosing the key of your song and one more for choosing your type of scale, such as major or minor. There is also a switch that allows you to choose whether the transition between pitch-corrected notes will be drastically computerized, semi-computerized or human-like. Auto-Tune EVO has two editing modes, each with a detailed series of knobs and menus that allow it to go much more in-depth than EFX.
The only thing EFX can do besides correct pitch is add the very popular "T-Pain" effect, technically called "Hard EFX" or "Soft EFX." These are the only two possible settings for the computerizing of the voice. In EVO, you get to choose on a scale of 1 to 100 how obvious an effect will be, and there are many more specific elements of the effect that can be changed. These include humanizing elements, natural vibrato, throat length, how quickly the effects will take place and much more.
EFX has no edit modes at all. Everything is automatically done. This means that EFX will choose the closest note in your selected key to correct each note to, so if your singer is too off-key, EFX will not correctly fix your pitch. EVO comes with a "Graph" mode, which turns off the automatic component of Auto-Tune and lets you edit the pitch frequencies manually. This is the preferred way of using Auto-Tune for professionals because you do not have to edit every note, and the notes you do edit are guaranteed to be exactly the pitch you want them to be.