Organistrum (or Hurdy-Gurdy) is a stringed instrument where traditional bow has been replaced with a wheel and crank and typical neck replaced with a mechanical box with buttons.
Typical Hurdy-Gurdy have one or two melodic strings (Chantelle) and 2 to 4 drone strings called Bourdons. Most of French versions of that instrument have additional "buzzing" string named Trumpette which produces rhythmical sounds especially useful in dance music.

Wheeled Fiddle (another name of the same instrument) has been played on courts in Medieval Ages and along centuries become popular folk instruments also among peasants. Many Hurdy-Gurdy players were wandering troubadours and minstrels who travel from one village to another entertaining people during weddings and other feasts.
In a times of French Revolution this instrument has been forgotten among aristocracy as unable to play multiple chords progression and was limited to a single drone chord.
Hurdy-Gurdy is typical European instrument and have various specific versions in many European countries.

My instrument have two melodic strings and 3 drones - has been handcrafted by one of most experienced Polish hurdy-gurdy makers - Stanislaw Wyzychowski.