Breaking: Acclaimed Singer Songwriter David Olney Dies On Stage at Florida Festival
He died during his third song, he stopped playing, said "I'm sorry" and collapsed. The video below was filmed the same day he died of what appears to be a massive heart attack.
Partial write up from Wikipedia: Olney performed as a solo singer-songwriter, and released more than 20 albums over four decades, including 6 live recordings. He collaborated with artists such as John Hadley and Sergio Webb. His songs were covered by and co-written with Emmylou Harris,Steve Earle,Linda Ronstadt,Steve Young,Del McCoury, and Laurie Lewis, among others.