Composers have used variations in music for centuries. In the Renaissance and Baroque periods composers wrote variations on a short tune in the bass which was repeated again and again. This was called a ground bass or sometimes it was a passacaglia or chaconne. Renaissance composers also liked writing what they called “divisions”. This meant varying a tune by playing it, for example, at twice the speed or half the speed etc. so that crotchets (quarter notes) became minims (half notes) or quavers (eighth notes).