History buffs with an interest in classical music have received a remarkable windfall. The New York Philharmonic has been digitizing its capacious archives, and the orchestra recently went live with its first installment, covering the years 1943 to 1970.
Take a look at what's now easily accessible. With the BSO soon to tackle Mahler's Ninth Symphony, I flipped through Bernstein's own conducting score this morning. You can see his technical comments (like this one, from the final page) as well as his own pointed philosophical reflections, scrawled longhand in the margins and blank pages. You can even examine the score while listening to a Bernstein-led performance from a 1965 radio broadcast.
Elsewhere in this online archive there are program scans as you'd expect (here, for example, is pianist Russell Sherman's debut). But there are also discoveries that may catch you by surprise. I stumbled rather chillingly upon Bruno Walter's last will and testament.