I had a chance to hear Beethoven's Sonata No 17 in D Minor,
Op.31, no 2 "The Tempest" in performance.
I love the idea of D Minor as the saddest key/Dorian mode etc etc and this was a piece on my list to hear.
It was lovely, but I did not find it particularly sad in feeling, nor do I consider Shakespeare's The Tempest, upon which it is apparently based, to be a sad play.
Kind of a disappointment, really. I love sad music.
I guess I should check and see if I can find someone else's list of D Minor music and work my way through it.
Actually, Widipedia says Mozart's Requiem is in D Minor - reason enough to call it the saddest key - as is Beethoven's 9th Symphony.
And my correspondent from months ago telling me that it is a Spinal Tap joke is correct - it is, but not original to them - Nigel Tufnel credits Mozart and Bach for inspiring his work in D Minor.
Meanwhile, Verdi's Requiem seems to be in G Minor, but Brahms's Requiem seems to be - yes! in D Minor (like his First Piano Concerto.)
Added note: I have added a link under Music Links to Wikipedia's (somewhat) incomplete explanation of Dorian mode, which also has a note about Aeolian mode, for anyone who is reading in the comments about Gorecki.
And: this Wikipedia article refers to The Beatles Eleanor Rigby, as a pop song in Dorian mode. It certainly makes sense for a song that is undoubtedly about loneliness and is perhaps the saddest Beatles song of all. Perfect.