The term 'chorale' is used to describe a musical form mainly used in German Christian Protestant church services. The chorale is a melody sung by the congregation and the sopranos, which is in turn harmonized by three lower voices. Given their utilitarian nature, they tend to be very singable tunes (even if the resulting harmonies are quite complex), and strophic in nature. Johann Sebastian Bach harmonized hundreds of chorales, which he set and the end of his Cantatas and Passions. Nowadays, chorales are also used as a device for studying harmonization.