Okay, this is a little music/library geeky, I admit, but have been wasting some time pleasantly perusing the New York Philharmonic online archive (part of an effort to get 8 million docs, 7000 hours of audio and video online). You can see Bernstein’s notes on Mahler scores, among many other gems. It’s a particularly good fit for this orchestra, which, particularly in the mid-century, was always forward looking about media and access.
Their promo video explains things nicely.
Check out May 14, 1959, the ground-breaking ceremony for Lincoln Center. Attended by the President of the United States, with performances by Risé Stevens and Leonard Warren. Back when classical music had more of a claim to being common cultural currency.