Halloween is coming up, so thoughts turn to playlists of scary, spooky music. But what makes a song that way? A long musical tradition that goes back to singing medieval monks. From Quartz:
Let’s face it. When it comes to creating a creepy Halloween atmosphere, the modern pop canon doesn’t have much to work with. Fortunately, ye olde Europeans liked their music a lot more chilling than “Thriller.” In fact, during the 18th century, it was composers like Franz Liszt and Richard Wagner who truly cracked the code of creepiness. The sonic dread they pioneered involved two key ingredients that horror movies and metal bands still use today: a forbidden sequence of notes known as “Satan in music,” and a spooky little ditty that Gregorian monks sang about the apocalypse.
Back in the Middle Ages, most Western music was written in praise of God—and was therefore supposed to sound pleasant. For composers of the day, that wasn’t a huge constraint. Take a C major scale—i.e. just the white keys on the piano—plunk out any two-note combination, and you’ll find they’re all holy ghost-grade harmonies.
Played in sequence or together, the notes F and B clash in a way that feels twitchy, unnatural, and foreboding. (If you don’t have a keyboard handy, think of the first two notes of Jimi Hendrix’s “Purple Haze” or Metallica’s “Enter Sandman”—or American police sirens.)
It’s this interval that folks in the dark ages and the Renaissance called diablous in musica—literally, ”Satan in music.” Modern music theorists know it as the tritone (as well as a diminished fifth, or an augmented fourth), though it’s also called the devil’s interval or the devil’s triad.