"He is one of the greatest actors of this or any time," remembered the show's creator, David Chase. "A great deal of that genius resided in those sad eyes. I remember telling him many times, 'You don't get it. You're like Mozart.' There would be silence at the other end of the phone."
And like all great artists, Chase acknowledged, "He wasn't easy sometimes. But he was my partner, he was my brother in ways I can't explain and never will be able to explain."
Gandolfini's Sopranos costar Steven Schirripa, who played Bobby Baccalieri, said: "Jimmy was a dear friend and like a brother to me. He was a great actor and a great father. I will miss him terribly. I am very sad."
And Steven Van Zandt, who played Silvio Dante on the HBO drama, Tweeted on Wednesday night, "I have lost a brother and a best friend. The world has lost one of the greatest actors of all time. Maureen and I send our deepest sympathy and love to Deborah, Michael, Lily, and all of Jimmy's family."
Celebrity chef Mario Batali, who was the actor's roommate at Rutgers University, told PEOPLE in a statement, "I am totally shocked and devastated by the passing of one of my oldest and dearest friends. I only hope to help his family any way I can in their grief and mourning."
His managers, Mark Armstrong and Nancy Sanders, who along with HBO confirmed Gandolfini's death in Italy, said, "Our hearts are shattered and we will miss him deeply. He and his family were part of our family for many years and we are all grieving."
Gandolfini is survived by his wife Deborah Lin, their 8-month-old daughter Liliana, and son Michael, 13, from a previous marriage.
"For Deborah and Michael and Liliana this is crushing," said Chase. "And it's bad for the rest of the world."