They use autotune as an artistic choice, they can both sing. The difference between autotune and pitch correction is their preciseviness; pitch correction is used by many of todays producers to fix slight intonation mistakes and autotune is used to shift your intonation into the closest scale. T-Pain can sing but uses autotune as his trademark because it makes his sound unique, just like the boys on Forget It and Sold My Soul To Satan Waiting In Line At The Mall
i'm fucking broken....i'm fucking broken again.. and i know never to forget my foes my friends are the same in the end i hope i regret leaving both when i am dead....