T-Pain says a criticism from Usher sent him into 4-year depression

Autotune helped T-Pain make multiple hits, but it also led to a dark period in his life.

In a clip from the upcoming Netflix series "This Is Pop," the rapper and producer says he was depressed for four years after Usher criticized him for using Autotune.

The music effect became very popular in the late '90s to alter voices.

T-Pain used it in several songs that topped the charts like "Blame It" and "Low."

Usher has not responded to requests for comment.

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