I use Melodyne for some singers.. I prefer not to use it.. To me it does a better job than auto tune.. (only my opinion, no offense to others)...

I prefer not to use pitch correctors.. I'm old.. when I was a kid we had to learn everything... slow that record player down, hum the solo, figure out the notes, do section by section speed back to normal...

I find so many young singers 20-30.. whose attitude, that's the way I sang it.. I don't like to rehearse, it takes away the spontaneity of my performance,, use autotune, or melodeon to fix it.. in fact they are undisciplined and and lazy.

Since I'm retired now, and no longer earning a living from music, I send those singers away. If I spent 20 hours getting the music right, trying ideas, etc.. I expect the singer to put in an equal amount of work.. ..

if time is short, and the pitch mistake not bad, I'll fix with melodyne,, but once I hear auto tune or melodyne on a singer, I automatically lose about 25 % or more of interest in the song.

Mellodyne and autotune are great for teaching a singer to improve, when they see their flat intros, swerve up to key , then overshoot it.. or the obnoxious vibrato a lot of singers use for any note longer than a 1/4.. They can improve just by singing, watching the pitch value vibrato, consonants etc. they can improve a lot quicker..

A tape recorder is a great teacher, with pitch recognition and illustration software,, a singer can make vast improvements.. My suggestion is to take a difficult melody section, sing it slower alone, no accompianent visualize the steps, take care to land right on the note not overshoot it, or slife up into to it. don't slap a vibrato onto every note,that gets boring real fast. it.. keep the tone pure.. when you can do it, bring the tempo up to speed.. decide where you want to slide into a note, where you want to flatten the end of a note.. and learn to gradually increase the strength of your vibrato, and learn to control the speed of it.. 90% of bad singers have one setting for vibrato, it instantly turns on/off and has only one speed.. You want the speed to of the vibratro to complement the music. it doesn't necessarily have to be in sync with it, also learn to control how sharp and flat you go..

The human voice is the greatest instrument of all.. And someone who can control all the various aspects of it, is a treasure.