Donovan's "Hurdy Gurdy Man" may be the creepiest song ever written about an obscure medieval instrument, but the Hurdy Gurdy did not give his recording its ominous sound. Those droning notes come from an Indian tanpura. Yet they evoke the title instrument, an ingenious musical invention set up primarily for the purpose of making drones. In the Middle Ages, it was known in Latin as the organistrum and the symphonia, and in French as the vielle à roue (the vielle with the wheel).
With a sound produced by a rosined wooden wheel, turned by a crank that set a number of strings in continuous droning vibration, the hurdy gurdy can, it's true, give off a bit of a folk horror vibe. From its very early, maybe 10th or 11th century origins in liturgical music, hurdy gurdy the instrument became associated with European folk music, shrinking from a beast played by two people to more portable dimensions, about the size of a large guitar and resembling a hand-cranked violin with keys for playing melodies on certain strings.
Though it grew smaller and more maneuverable, however, the instrument grew no less complicated. It's been called the equivalent of a medieval spaceship with its more than 80 moving parts.