Wikipedia article

Jonathan Melvoin, born December 6, 1961, was the Pumpkins touring keyboardist on the Mellon Collie tour in 1995-96. On July 12, 1996, he died of a heroin overdose. Pumpkins drummer Jimmy Chamberlin, who was also present, tried to revive him but was unsuccessful.

Following Jonathan's death, Jimmy was fired from the band and forced to enter drug rehab. He re-joined the band in 1999 for the Arising! tour.

Jonathan can be seen playing the piano in in the Pumpkins' "Zero" music video, and had also done work with The Dickies, Wendy & Lisa Project, and Prince & the Revolution.