Blake Shelton landed a very special singer on his team for Season 21 of The Voice on Tuesday night (Sept. 28). The country superstar chose to coach an aspiring country singer with an incredibly difficult backstory, who told him, "It's a dream come true."

Berritt Haynes is a 19-year-old Alabama native who auditioned for the coaches by singing Brett Young's "Mercy" in an audition that left Shelton raving about his voice.

Haynes performed an acoustic version of "Mercy," and while his strong vocal performance was enough to land him a slot on Shelton’s team, his backstory sparked more interest.

Haynes was diagnosed at the age of 8 with Hypertrophic Cardiomyopathy, which is also called "sudden death disease." Hypertrophic Cardiomyopathy, according to the Mayo Clinic, "is a disease in which the heart muscle becomes abnormally thick (hypertrophied). The thickened heart muscle can make it harder for the heart to pump blood."

Six years after Haynes' diagnosis, an implantable cardioverter-defibrillator (ICD) was placed in his chest to help detect and control irregular heartbeats.

His audition left Shelton stunned.

Season 21 of The Voice premiered on Sept. 20, and Shelton has been building a strong team. He scored a very powerful singer in the first night with Wendy Moten, who auditioned with the Beatles' "We Can Work It Out." Her audition drew a four-chair turn from Shelton, Clarkson, John Legend and Ariana Grande, and Shelton praised it as "a top three blind audition for The Voice, all time."

Shelton took on 19-year-old Peedy Chavis later that night after he auditioned with Elvis Presley's "Heartbreak Hotel," and he scored country singer Lana Scott the following night after she auditioned with Kelsea Ballerini's "Hole in the Bottle."

Shelton also added a country trio called the Joy Reunion to his team on Monday night (Sept. 27), as well as 17-year-old country singer Carson Peters.

The Voice airs Monday and Tuesday nights at 8PM ET on NBC.

WATCH: Has The Voice Changed Blake Shelton?

The Voice Stars, Then + Now:

More From TheBoot