A chorale is a musical composition for voices, typically sung in a four-part harmony, and often accompanied by instruments. Chorales are typically religious in nature, and are often used in church services. The term "chorale" can also refer to a choir or group of singers who perform chorales.
The most famous chorales are the ones written by Johann Sebastian Bach, who was the Kantor of the Thomaskirche in Leipzig from 1723 until his death in 1750. Bach wrote over 300 chorales, many of which are still performed today.