Saoirse Ronan actually played Ludwig van Beethoven's complicated Piano Sonata Opus 2, No. 3, having undergone an intense twelve-week crash course in piano lessons.
The ancient shrine where the vampires are made was filmed on Skellig Michael off the Irish coast. This is the same location used for Luke's refuge in Star Wars: O Despertar da Força (2015) and Star Wars: Os Últimos Jedi (2017).
The seaside town used as the location of this movie was Hastings, East Sussex, England.
The main piano music throughout the film, and the one that Saoirse Ronan actually plays an extract from, is from Ludwig van Beethoven's third piano sonata, Opus 2, Number 3, in C major, written from 1794-95. It is one of three piano sonatas in the Opus 2 set of piano sonatas, which was his second published work. The whole Op. 2, No. 3 sonata consists of four separate movements, taking about 20-25 minutes to play in entirety. The part Saoirse Ronan plays in the movie is the minor key second theme from the slow second movement (Adagio). Contrary to ubiquitous news stories, she did not "master the entire sonata" in 12 weeks, as that would be extremely difficult if not impossible for even advanced musicians. This ridiculous claim diminishes her actual achievement, as the extract she does play is still musically challenging, though nowhere near the difficulty level of the other three movements of the sonata.
In 1816, Lord Byron, Percy Bysshe Shelley, Mary Wollstonecraft Shelley, Claire Clairmont, and John Polidori gathered at the Villa Diodati on Lake Geneva, Switzerland, in the fabled "haunted summer", which has been depicted in several movies. In a drug and alcohol-induced frenzy, they engaged in a contest to see who could write the best ghost story. Mary Wollstonecraft Shelley produced "Frankenstein, or the Modern Prometheus". Byron began a vampire story, but abandoned it out of boredom. Polidori picked it up and created "The Vampyre" (the forerunner to "Bram Stoker's Dracula"), whose title character, Ruthven, was modelled on Byron. Jonny Lee Miller portrayed a character named "Ruthven" in this movie and the title role in the biopic, Byron (2003).