Johann Sebastian Bach is considered by many to be the greatest composer who ever lived. A master of the Baroque era, his music is the pinnacle of 'counterpoint'—the art of weaving multiple independent melodies together. Bach spent much of his life working as a church musician, and much of his output was religious, including the 'St. Matthew Passion' and his nearly 200 cantatas. He was also an expert on the organ and harpsichord. His 'Well-Tempered Clavier' was a foundational work that explored the use of all 24 major and minor keys. Interestingly, Bach was not widely famous during his lifetime and was seen as somewhat old-fashioned. It wasn't until the 19th-century 'Bach Revival,' led by Felix Mendelssohn, that his true genius was recognized globally. His music is seen as a perfect blend of mathematical logic and profound emotion.