(through the French from Lat. con-, with, and certare, to strive), a term meaning, in general, co-operation, agreement or union; the more specific usages being, in music, for a public performance by instrumentalists, vocalists or both combined, and in diplomacy, for an understanding or agreement for common action between two or more states, whether defined by treaty or not. The term "Concert of Europe" has been commonly applied, since the congress of Vienna (1814-1815), to the European powers consulting or acting together in questions of common interest. (See ALLIANCE and EUROPE: History.)