I'm doing a pre-concert talk at the Wigmore Hall on 26 January about three of Mozart's greatest string quartets, the last half of the six he dedicated to Haydn, which the Hagen Quartet will be performing that night. I've been swotting. And it's heaven.
If you listen to only one piece today, make it this: the slow movement of the C major Quartet K465, the 'Dissonance'. Here's the Ebène Quartet playing it. I find it deeply saddening that there are thousands, millions, of people in western 'democracies' who will go through their entire lives without hearing music of such phenomenal beauty because they've been taught to imagine that it is 'not for them'.
If you have never heard this piece before, I hope your day is lit from within by it. And if you know it well - likewise. Then please sit one person down and get them to listen to it too.