When Glenn Gould died unexpectedly in 1982, a victim of a stroke at the unseemly age of 50, his red-hot reputation had calmed to a simmer. Gould, a sufferer from extreme stage fright but a winner in the stock market, had quit performing in public 18 years earlier, using the proceeds of his financial ventures to soften the burdens of early retirement. Much of his time later was spent with television projects in his native Toronto, not all of which had to do with the piano. In death, Gould came to life. Music business operatives appeared suddenly and in hordes,...