Bach, Johann Christian (krĭs`tyän bäkh), 1735–82, German musician and composer; son of J. S. Bach. He went to Italy in 1754, became a Roman Catholic, and composed church music and operas. In 1760 he became organist of the Milan Cathedral. Two years later he went to England, where he became music master to the royal family. A popular and highly prolific composer in the rococo style, he influenced the young Mozart.