will.i.am has been talking about why he relies on Auto-Tune so much and it's basically because he can't sing.
Talking to Alan Carr (as quoted here), i.am explained: "I use Auto-tune because I write and produce. A lot of the time I am in the studio by myself and no one works as much as I do."
"So the computer allows me to make music singing myself and not wait around for singers to come and sing it," he continued.
"It's a rare combination to have someone who can write songs and sing well," said the man who's worked with Cheryl Cole.
"The computer allows me to execute my ideas at the speed I think them. So that's why I learnt to (use) Auto-Tune. It's just an effect. But I am working on, you know, my singing abilities."