T-Pain says remarks from fellow musician Usher ushered in years of pain. In the upcoming Netflix series This Is Pop, T-Pain says he fell into a four-year depression after Usher criticized his use of Autotune, saying he had "really f---ed up music for real singers," Entertainment Weekly reports. T-Pain popularized the use of the technology in hip-hop, starting with his 2005 hit "I'm Sprung," reports USA Today. He says Usher was a friend he respected and he initially thought the R&B singer was joking. "I'm like, 'But I used it, I didn't tell everybody else to start using it,'" T-Pain says. "I don't even think I realized this for a long time, but that's the very moment that started a four-year depression for me." (More T-Pain stories.)