'La Follia di Spagna' is a well-known tune that...

Lots of different composers have set or adapted, as described here: apparently it is more the case that "the essence of the 'early Folia' was not a specific theme or a fixed sequence of chords but rather a compositional-improvisational process which could generate these sequences of chords"-- indeed, sure, sure; having had no idea before two minutes ago that there were earlier and later 'Folies d'Espagne' all of that is rather more than I am interested in knowing this morning.

The point was to mention that I'm listening to a newly-released recording of Antonio Salieri's 26 Variazioni sull'Aria La Follia di Spagna; the album is entitled Beethoven's World and includes pieces also of Hummel and Vorisek.

And here is the Sarabande from Handel's Keyboard Suite in D minor HWV 437.

There was a second point as well but at this point it has escaped my mind. Time for Terce, in any case, and then breakfast.