82-year-old John Hetlinger, who became a viral video sensation last month when he belted out the (2001) DROWNING POOL classic "Bodies" on the NBC series "America's Got Talent", joined the band...to perform the song at the Chicago Open Air festival...

Hetlinger...was a Navy pilot...a minister and then an aerospace engineer...who worked on a team that made repairs to the Hubble telescope...(He) got hooked on karaoke after singing during talent shows on cruise ships in the '90s.

DROWNING POOL guitarist CJ Pierce said he first heard about Hetlinger's performance when family and friends starting texting him about it. "...Jasen Moreno is our (singer) right now. But if he doesn't work out, we always know we've got John on the back burner."

Despite being a huge rock radio smash, (Bodies) was removed from radio playlists for a while...in the wake of the September 11 terrorist attacks.