T-Pain is opening up about his four-year battle with depression.

In a clip from Netflix's series, This Is Pop, the rapper reveals the dark side of his musical success that included the infamous introduction of auto-tune to mainstream music.

Although the pitch correction technique has been around for ages and using it helped propel T-Pain to superstardom, the rapper claims it led to a confrontation with Usher, who allegedly told him that he "f**ked up music."

"Usher was my friend. I really respect Usher. And he said, 'I'm gonna tell you something, man. You kinda f**ked up music,'" T-Pain claims in the clip released by Entertainment Weekly on Monday. 

The rapper -- who also explains that the alleged conversation occurred during a plane ride -- says he thought Usher was joking at first, so he laughed. But, according to T-Pain, Usher allegedly doubled down on his comment and said that the rapper "really f**ked up music for real singers." 

"That is the very moment, and 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," T-Pain shares. 

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The rapper's use of auto-tune, which sparked a plethora of artists following his example, was quickly met with a wave of backlash. In 2009, JAY-Z even recorded an entire diss track attacking the pitch correction titled "DOA (Death of Auto-Tune)."

The backlash was so fierce that people seemed to forget that T-Pain was a genuinely talented musician and producer, a fact the rapper has spoken about many times before. During his Tiny Desk Concert for NPR, during which he sang entirely without the processor, the rapper joked that the auto-tune was "surgically inserted."

Since then, the rapper has gone on to win the first season of The Masked Singer, release a new album and co-write a cocktail book. 

This Is Pop is an eight-part series exploring untold stories from some of the biggest moments in pop music history. In addition to T-Pain, it features interviews with ABBA's Benny Andersson, Shania Twain, Brandi Carlile, Chuck D, Babyface, Orville Peck, Hozier, members of Boyz II Men, Backstreet Boys, Blur, and many more.