Real Dictionary

Mannheim School in American English
noun: a group of musicians of the mid-18th century in Mannheim, Germany, notable for developing a style of orchestral composition and performance directly antecedent to and influential on the classical style of Haydn and Mozart

Mannheim School in British English
noun: a group of musicians and composers connected with the court orchestra at Mannheim during the mid-18th century, who evolved the controlled orchestral crescendo as well as a largely homophonic musical style