Singers have always eyed heavier roles, wishing they had the equipment for them, and often trying them on for size. Nellie Melba famously attempted the Siegfried Brunnhilde, promptly lost her voice (temporarily), and admitted she'd been a fool. Beverly Sills joked that she was born with the voice of Beverly Sills and the mind of Birgit Nilsson, and although it shortened her career to take on Donizetti's queens and other dramatically satisfying parts, she and her audiences had no regrets. Netrebko's audiences seem happy too; those who can't tolerate what she's done to her voice are probably not paying to sit in those audiences. All of which leads up to pointing out that, although Freni and Scotto moved into what's considered spinto roles with essentially lyric voices, they had a better sense of their limits than Netrebko, who seems not to acknowledge any limits when she takes on Turandot and Isolde (I'm not sure whether she's sung the whole of Isolde yet, but her dreadful Liebestod is on YouTube). Scotto's voice gradually became strident on top, but she had the artistic sense not to turn herself into a wobbling foghorn like Netrebko.