Notyourmemories, while there is error-correction used when recording albums to save cost and time, the end goal is to have the singer's voices sound like the
singer's voices. It should work in the background, completely unnoticed.
For some reason, the creators of Glee (a show that supposedly celebrates singing) have decided to overuse the effect to the point where the voices deliberately sound synthesized. It is especially baffling as many in the cast can actually sing quite well. One of the few times I've seen the cast was on the Oprah appearance where they sang "live" and sounded absolutely amazing.
If the audience could do better, they'd be up here on stage and I'd be out there watching them. - Ethel Merman