My knowledge of classical music is rudimentary I'm sad to say. So I was glad to come across Jay Nordlinger's suggestions (via Between Two Worlds). Nordlinger offers listening suggestions to which I expect to refer quite a lot. It's not for the well-schooled, but for people like me. A reader of "Between Two Worlds" adds helpfully:
On a related note, NPR Music is running an online (weekly?) series called the The NPR Classical 50.
Two critics are listing the 50 essential classical recordings for
building a library. Each article has commentary and a significant
streaming sample (~20:00).