Used for "some of the hook and ad libs" on "Intro", as stated by Kirk mix engineer Kevin "Black Pearl" McCloskey in this December 2019 Sound on Sound interview.

"Some of the hook and ad libs audio tracks have the Antares Auto-Tune EFX, because Jon wanted a small amount of tuning to lock them in. It's on the default setting of 25 with Humanize at 100 percent, so it's not very noticeable. The main vocal don't have Auto-Tune."

Used for the vocals on "Old Town Road (Remix)", as stated by mix engineer Andrew "VoxGod" Bolooki in this August 2019 Sound on Sound interview. An image of the settings can be found here.

Bolooki's 'Old Town Road' session also has an incredibly [sic] amount of plug-ins. Most tracks have plug-ins on the inserts, in some cases up to six, and many tracks also have sends to the aux tracks. A complete analysis of exactly what they all do would take up several pages, so Bolooki selected some of the most important processors, starting with Nas X's tracks.

"I did not really mess much with what they sent me. If you listen to the original, there were some Auto‑Tune anomalies, because the plug-in had some notes out of scale. The key of the song is a little weird, so I had to do automation on Nas' Auto‑Tune EFX instances to bypass certain notes in certain passages, to make sure the AT did not warp notes in the wrong way. I also did a lot of vocal riding, nudging the volume of each phrase, so that every single word was crystal-clear, and I did some panning automation in the stacked parts. They wanted Billy and Nas to sing at the same time in the pre-choruses, and I wanted to prevent Billy's harmonies from overwhelming Nas' lead vocals, so I used panning to give them each their own space.

"All Nas X's vocal tracks have an insert effect chain that consists of Antares Auto‑Tune EFX, Avid EQ3 7-band, Waves SSL Channel, Waves Renaissance De-Esser and Waves L2. I made some basic changes, also to some of the delay and reverb sends, but nothing crazy. There's a lazy half-note delay in the intro of the song, that becomes part of the flow of the song, and I did not want to mess with that. The aux track with the AIR Phaser added some modulation in the pre-chorus, and the Waves RVox and UAD Precision K-Stereo made Nas' lead vocal stand out a bit more.

"Also, the original engineer who recorded Nas' vocals did something that I would not normally do, but that made a big difference. I picked it up as a trick. It's having the L2 hit really hard at the end of the effects chain for every single vocal track. Initially I thought: that is pretty extreme to put that on every single vocal track, and it breaks all the rules for gain-staging, so I took it off, but then I realised he had put it there for a saturation effect, and it greatly helped the tone of his vocal. It was part of Nas' sound."

In this YouTube breakdown video of LUCKY, Bad Snacks can be seen using Auto-tune EFX+ at 23:34. She mentions not being ashamed using it at 22:34.

Used sparsely for Ray's vocals on "Old Town Road (Remix)", notably for the outro whistle, as stated by mix engineer Andrew "VoxGod" Bolooki in this August 2019 Sound on Sound interview. An image of Lil Nas X's vocal chain specifies EFX+.

"I comp with only a click track, and sometimes I'll put a low-pass filter on the beat, playing at very low volume, so you only hear the bass in the background. I'll have very little or no Auto‑Tune on the vocals, because it's easier to comp without Auto‑Tune, and zero effects. The vocal will be entirely dry, apart from that I'll add a ton of compression, to bring up all the room and microphone noises. When you comp with the high end only coming from the vocals, you select takes not only on performance, but also on tone, particularly if they're bright. The brighter ones tend to have the best emotion, too. They may not be in time or in tune, but those things are fixable. I'll also do a lot of clip gaining when comping. When you comp in this way, by the time you're done, it's perfect. If you make the vocal sound good with just a click track, you know you have nailed it. Very little EQ is necessary, and then all you have to do is add some tasteful effects, and your vocal rides, as well as tuning and timing. But you don't have to cover up any of what you did."

(...) Bolooki explains that he makes frequent use of Celemony's Melodyne as well as Antares' Auto‑Tune. "I usually use both. My process depends on the song. For this song, I actually didn't use Auto‑Tune on Billy's verse at all. I am really proud of how hard he worked in the booth and how little tuning was needed. The Auto‑Tunes I used on some of his chorus tracks are extremely subtle and purposely on slow, automated retune speeds along with automated bypasses so they only kick in exactly when needed with the least amount of correction possible. There was really no stone left unturned when it came to his comps. I spent a ridiculous amount of time tediously combing through all of his takes down to the syllable, so little to no Auto‑Tune was necessary in the end.

"I used Melodyne to keep the timing of his doubled parts together, since they were all recorded separately. I always have Melodyne as the first insert, then basic EQ, de-essing, compression, and then Auto‑Tune if needed. I don't use the stand-alone version of Melodyne anymore, because I like to have Melodyne and Auto‑Tune running into each other at the same time. When I have Auto‑Tune after Melodyne, I tend to not over-tune things, because for me Melodyne is basically just a timing tool. Pitch-wise you have more flexibility with Melodyne than Auto‑Tune, but each has their own strengths. Also, Melodyne purposely does not make things perfect, which I like. When you stack vocals and use Melodyne for adjustments, even corrected vocals will stay somewhat naturally out of tune with each other. So instead I focus mostly on timing in Melodyne, and keep Auto‑Tune on after it, set to a slow retune speed, and I use the Flex-Tune knob quite a bit to allow a lot of humanising."