Der Messias, K. 572, is Wolfgang Amadeus Mozart's 1789 German-language version of the 1741 oratorio, "Messiah", by which German, later British, baroque composer who spent the bulk of his career in London, becoming well known for his operas, oratorios, anthems, and organ concertos, and received important training in Halle and worked as a composer in Hamburg and Italy before settling in London?