As our dance of folly made its way into the Romantic Age, it was (as ever) the virtuosos who kept its flame burning proudly. So we get Les folies d'Espagne et un menuet for solo guitar by the Spaniard Fernando Sor (1778-1839), another Les Folies d'Espagne for solo guitar by the French composer François de Fossa (1775-1849) and, best of all, a concerto movement based on the theme by the great violin virtuoso Niccolò Paganini (1782-1840), namely the Rondo ossia Polonese finale from the Violin Concerto No.6 in E minor.
A surprise here is the presence of a set of variations for solo guitar, La Folia, by Hector Berlioz. Who would have expected that? It is, however, one of his earliest pieces and was only discovered a couple of decades ago. (It's no masterpiece).
The greatest of all the 19th Century virtuosi, Franz Liszt, contributed one of the best-known pieces based on La Folia, his Rhapsodie espagnole. A second Spanish tune, Jota Aragonese, is also varied during the course of this immensely likeable piece.
Here's another intriguing one, one of Edvard Grieg's Norwegian Melodies - In Rosenlund During Saga Times (Under The Spell Of The Sagas... ) - seems to bear the influence of La Folia, probably because many a Scandinavian folktune (apparently) seems to have been influenced by the old melody.
The tune wasn't finished yet. The 20th Century saw some of its richest reincarnations.