VoxDoubler: Vocal Doubling Plugin by Sonnox

Widen generates two new mono voices and pans them to the left and right of the original vocal. It suits widening a mono performance, from a subtle enhancement to a stack of hard-panned voices. You can also process the new doubled voices separately and mix them back in parallel with the original.

Thicken generates a new stereo doubled voice and overlaps it with the original. It can thicken a mono performance, emulating the effect of singing the same part twice, or thicken a stereo group of voices by doubling each one.

The Humanise section adjusts the timing and pitch of the doubles relative to the original vocal. A Depth control pushes the new doubled voices deeper into the mix. A Tone control stops sibilant doubles from becoming distracting, or brightens doubles that sound muddy.

Track/Aux mode lets you apply the effect in place on a track, or mix it in parallel on an aux return for more advanced control.