Rachmaninoff's Prelude in C# minor. I remembering first hearing this and having such a sense of foreboding, as if it were the essence of an Edgar Allen Poe story set to music. I then later learned that it was inspired by a dream Rachmaninoff had where he was at a funeral and as he approached the coffin, he began feeling more and more terrified and anxious until he finally sees who is in it... him of course! So my initial impression was right after all.