Vocal producer Simone Torres turns a single voice into a convincing choir, walking through a session from one of her own songs. The trick is refusing to sound like herself twice. She varies vibrato speed, vowel shape, and tonal character on purpose. So the vocal layers stop feeling stacked and start feeling like a room full of people.
She uses different voice characters (brighter, deeper, breathier), varying distances from the mic, and intentional randomness in phrasing and note choices. Some layers move against the melody, and a few are almost accidental. That unpredictability sells the illusion of a real ensemble.
For the high end, she adds thin airy layers you barely hear. Those parts create a sense of openness and extra space. For a rawer, chanty section of the song, she runs character voices through Decapitator for distortion and grit. She also mirrors an organ part with a vocoder layer.