GSnap is the first-ever free autotune VST plugin. It was the first freeware VST plugin that was able to achieve the classic autotune effect. Back in the day, such software tools were still somewhat of a rarity.
In terms of its features and design, GSnap is still a fantastic pitch correction plugin. At first look, it seems very similar to Graillon 2 and MAutoPitch. One excellent feature that sets it apart, though, is the ability to tune the processed audio signal according to the MIDI notes on the input. In other words, you don’t have to rely on the plugin’s automatic pitch detection algorithm. Instead, the user can feed the correct MIDI notes into the plugin and let it take care of the rest. GSnap’s automatic pitch detection algorithm does a great job as well, although without the formant shifting features found in Graillon 2 and MAutoPitch.
Unlike Graillon 2 and MAutoPitch, GSnap will only work on Windows-based systems. It does come with a very well-written manual, though. The instructions are worth a read if you decide to use GSnap as your go-to pitch correction tool.
Download: GSnap (32-bit & 64-bit VST plugin format for Windows)